RATE AND REGULATORY MATTERS

Below is a summary of significant regulatory proceedings and related lawsuits. We are unable to predict the ultimate outcome of these matters, the timing of the final decisions of the various agencies and courts, or the effect on our results of operations, financial position, or liquidity.

Missouri

2014 Electric Rate Case

In July 2014, Ameren Missouri filed a request with the MoPSC seeking approval to increase its annual revenues for electric service. The request, as amended in February 2015, seeks an annual revenue increase of approximately $190 million. The amended rate request seeks recovery of increased net energy costs and rebates provided for customer-installed solar generation, as well as recovery of, and a return on, electric infrastructure investments. Approximately $100 million of the amended request relates to an increase in net energy costs above the levels included in base rates authorized by the MoPSC in its December 2012 electric rate order. Absent initiation of this general rate proceeding, 95% of those costs would have been reflected in rate adjustments implemented under Ameren Missouri’s existing FAC. The amended electric rate increase request is based on a 10.4% return on common equity, a capital structure composed of 51.8% common equity, an electric rate base of $7 billion, and a test year ended March 31, 2014, with certain pro forma adjustments through true-up dates of December 31, 2014 and January 1, 2015.

Ameren Missouri's rate request also seeks continued use of the FAC and the regulatory tracking mechanisms for storm costs, vegetation management and infrastructure inspection costs, pension and postretirement benefits, and uncertain income tax positions that the MoPSC authorized in earlier electric rate orders.

In October 2014, as part of this rate case proceeding, the MoOPC, the MIEC, and other parties filed a rate shift request that seeks to reduce Noranda’s electric rates with an offsetting increase in electric rates for Ameren Missouri’s other customers. Ameren Missouri supplies electricity to Noranda’s aluminum smelter in southeast Missouri under a 15-year agreement, that is subject to termination as early as 2020 upon at least five years notice by either party. Termination of the agreement by Ameren Missouri would require MoPSC approval.

In February 2015, the MoPSC staff recommended an increase to Ameren Missouri's annual revenues of $89 million based on a return on equity of 9.25%. In addition, the MoPSC staff opposed the continued use of the regulatory tracking mechanisms for storm costs and vegetation management and infrastructure inspection costs. The MoPSC staff also opposed the recovery of $36 million in fixed costs not previously recovered associated with the accounting authority order discussed below.

The MoPSC proceedings relating to the proposed electric service rate increase are ongoing and a decision by the MoPSC is expected by May 2015, with new rates effective by June 2015. Ameren Missouri cannot predict the level of any electric service rate change the MoPSC may approve or whether any rate increase that may eventually be approved will be sufficient for Ameren Missouri to recover its costs and to earn a reasonable return on its investments when the rate changes go into effect.

FAC Prudence Review and Accounting Authority Order

In July 2013, the MoPSC issued an order with respect to its review of Ameren Missouri’s FAC calculation for the period from October 1, 2009, to May 31, 2011. In this order, the MoPSC ruled that Ameren Missouri should have included in the FAC calculation all revenues and costs associated with certain long-term partial requirements sales that were made by Ameren Missouri because of the loss of Noranda's load caused by a severe ice storm in 2009. As a result of the order, in 2013 Ameren Missouri recorded a pretax charge to earnings of $26 million, including $1 million for interest, for its estimated obligation to refund to its electric customers the earnings associated with these sales previously recognized for the period from October 1, 2009, to May 31, 2011. Ameren Missouri recorded the charge to “Operating Revenues – Electric” and the related interest to “Interest Charges” with a corresponding offset to “Current regulatory liabilities.” No similar revenues were excluded from FAC calculations after May 2011.

Separately, in July 2011, Ameren Missouri filed a request with the MoPSC for an accounting authority order that would allow Ameren Missouri to defer fixed costs totaling $36 million during the time period of March 1, 2009, to May 31, 2011, not previously recovered from Noranda as a result of the loss of load caused by the severe 2009 ice storm, for potential recovery in a future electric rate case. In November 2013, the MoPSC issued an accounting authority order that allowed Ameren Missouri to seek recovery of these fixed costs in an electric rate case. Ameren Missouri’s July 2014 electric rate case filing requested recovery of these fixed costs over five years. The MIEC and the MoOPC filed appeals of the MoPSC’s November 2013 accounting authority order with the Missouri Court of Appeals, Western District. In January 2015, the Missouri Court of Appeals, Western District upheld the MoPSC's order. Ameren Missouri has not recorded any potential revenue associated with this accounting authority order.

MEEIA Filing

In December 2014, Ameren Missouri filed an energy efficiency plan with the MoPSC under the MEEIA. This filing proposed a three-year plan that includes a portfolio of customer energy efficiency programs along with a cost recovery mechanism. If the plan is approved, beginning in January 2016, Ameren Missouri intends to invest $135 million over three years in the proposed customer energy efficiency programs. Ameren Missouri requested continued use of a MEEIA rider that allows it to collect from or refund to customers any difference in the actual amounts incurred and the amounts collected from customers for the MEEIA program costs and its lost revenues. In addition, Ameren Missouri requested incentives to earn additional revenues by achieving certain energy efficiency goals, including $25 million if 100% of its energy efficiency goals are achieved during the three-year period. Ameren Missouri must achieve at least 70% of its energy efficiency goals before it earns any incentive award.

Illinois

IEIMA

Under the provisions of the IEIMA, Ameren Illinois’ electric delivery service rates are subject to an annual revenue requirement reconciliation to its actual costs. Throughout each year, Ameren Illinois records a regulatory asset or a regulatory liability and a corresponding increase or decrease to operating revenues for any differences between the revenue requirement reflected in customer rates for that year and its estimate of the probable increase or decrease in the revenue requirement expected to ultimately be approved by the ICC based on that year's actual costs incurred. As of December 31, 2014, Ameren Illinois had recorded regulatory assets of $101 million and $65 million to reflect its expected 2014 and 2013 revenue requirement reconciliation adjustments, respectively, with interest. As of December 31, 2013, Ameren Illinois had recorded a $65 million regulatory liability to reflect its 2012 revenue requirement reconciliation adjustment, which was refunded, with interest, to customers during 2014.

In December 2014, the ICC issued an order in Ameren Illinois’ annual update filing approving a $204 million increase in Ameren Illinois’ electric delivery service revenue requirement beginning in January 2015. This update reflects an increase to the annual formula rate based on 2013 actual costs and expected net plant additions for 2014, an increase to include the 2013 revenue requirement reconciliation adjustment, which was recorded as a regulatory asset at December 31, 2014, and an increase resulting from the conclusion of the 2014 refund to customers for the 2012 revenue requirement reconciliation adjustment.

In February 2014, Ameren Illinois filed an appeal of the ICC's December 2013 annual formula rate order to the Appellate Court of the Fourth District of Illinois regarding the rate treatment of accumulated deferred income taxes related to the transfer of former Ameren Missouri electric assets located in Illinois to Ameren Illinois. Ameren Illinois withdrew this appeal in February 2015.

In the December 2013 order, the ICC disallowed, in part, the recovery from customers of the debt premium costs paid by Ameren Illinois for a tender offer in August 2012 to repurchase outstanding senior secured notes. As a result of the ICC order, in 2013, Ameren and Ameren Illinois each recorded a pretax charge to earnings of $15 million relating to the partial disallowance of the debt premium costs. In the December 2014 order discussed above, the ICC allowed partial recovery from customers of certain previously disallowed debt premium costs. Accordingly, in 2014, Ameren and Ameren Illinois each recorded a pretax increase to earnings of $11 million to reflect the partial recovery of the debt premium costs. Ameren and Ameren Illinois recorded the effects of both orders to “Interest charges” with a corresponding offset to “Regulatory assets.”

2015 Natural Gas Delivery Service Rate Case

In January 2015, Ameren Illinois filed a request with the ICC seeking approval to increase its annual revenues for natural gas delivery service by $53 million. The request was based on a 10.25% return on common equity, a capital structure composed of 50% common equity, and a rate base of $1.2 billion. In an attempt to reduce regulatory lag, Ameren Illinois used a 2016 future test year in this proceeding. Included in the request was a proposal to implement a decoupling rider mechanism for residential and small nonresidential customers. The decoupling rider would ensure that changes in natural gas sales volumes do not affect Ameren Illinois' annual natural gas revenues for these rate classes.

A decision by the ICC in this proceeding is required by December 2015, with new rates expected to be effective in January 2016. Ameren Illinois cannot predict the level of any delivery service rate changes the ICC may approve, or whether the ICC will approve the decoupling rider, or whether any rate changes that may eventually be approved will be sufficient to enable Ameren Illinois to recover its costs and to earn a reasonable return on investments when the rate changes go into effect.

2013 Natural Gas Delivery Service Rate Order

In December 2013, the ICC issued a rate order that approved an increase in revenues for Ameren Illinois' natural gas delivery service of $32 million. The revenue increase was based on a 9.1% return on common equity, a capital structure composed of 51.7% common equity, and a rate base of $1.1 billion. The rate order was based on a 2014 future test year. The rate changes became effective January 1, 2014. In March 2014, Ameren Illinois filed with the Appellate Court of the Fourth District of Illinois an appeal of the allowed return on common equity included in the ICC's order and also appealed the rate treatment of accumulated deferred income taxes related to the transfer of former Ameren Missouri natural gas assets located in Illinois to Ameren Illinois. Ameren Illinois sought a 10.4% return on common equity in this rate case. In February 2015, Ameren Illinois withdrew its appeal solely as it related to the rate treatment of the accumulated deferred income taxes.

ATXI Transmission Project

ATXI's Spoon River project in northwest Illinois is a MISO-approved transmission line project with an expected cost of $150 million. In August 2014, ATXI made a filing with the ICC requesting a certificate of public convenience and necessity and project approval for the Spoon River project. A decision is expected from the ICC in 2015. A certificate of public convenience and necessity is required before ATXI can proceed with right-of-way acquisitions.

Federal

2011 Wholesale Distribution Rate Case

In January 2011, Ameren Illinois filed a request with the FERC to increase its annual revenues for electric delivery service to its wholesale customers. These wholesale distribution revenues are treated as a deduction from Ameren Illinois’ revenue requirement in retail rate filings with the ICC, with no material effect on net income. In March 2011, the FERC issued an order authorizing the proposed rates to take effect, subject to refund when the final rates are determined. In September 2014, the FERC issued an order that finalized rates and resulted in refunds due to the wholesale customers. In October 2014, Ameren Illinois refunded $24 million, including interest, to the wholesale customers and requested a rehearing on certain aspects of the order.

Ameren Illinois Electric Transmission Rate Refund

In July 2012, the FERC issued an order concluding that Ameren Illinois improperly included acquisition premiums, including goodwill, in determining the common equity used in its electric transmission formula rate and thereby inappropriately recovered a higher amount from its electric transmission customers. The order required Ameren Illinois to make refunds to customers for such improperly included amounts. In August 2012, Ameren Illinois filed a request for a rehearing of this order.

Ameren Illinois submitted a refund report in November 2012 and concluded that no refund was warranted. Several wholesale customers filed a protest with the FERC regarding that conclusion. In June 2013, the FERC issued an order that rejected Ameren Illinois' November 2012 refund report and provided guidance as to the filing of a new refund report. In July 2013, Ameren Illinois filed a revised refund report based on the guidance provided in the June 2013 order, as well as a request for a rehearing of that order. Ameren Illinois' July 2013 refund report also concluded that no refund was warranted.

In June 2014, the FERC issued an order that denied Ameren Illinois’ rehearing requests of the July 2012 order and the June 2013 order. Separately, in June 2014, the FERC issued an order establishing settlement procedures and, if necessary, hearing procedures regarding Ameren Illinois’ July 2013 refund report. In July 2014, Ameren Illinois filed an appeal of the FERC order denying rehearing of the July 2012 and June 2013 orders with the United States Court of Appeals for the District of Columbia Circuit. Also in July 2014, Ameren Illinois filed a request for rehearing with the FERC of its June 2014 order regarding the July 2013 refund report. In November 2014, the United States Court of Appeals for the District of Columbia issued an order suspending the appeal until the related FERC proceedings have been completed.

Ameren Illinois estimates the maximum pretax charge to earnings for this possible refund obligation through December 31, 2014, is $22 million. Ameren and Ameren Illinois recorded a current liability representing their estimate of the probable refund due to electric transmission customers based on the June 2014 order. If Ameren Illinois was to determine that a refund to its electric transmission customers in excess of the amount already recorded is probable, an additional charge to earnings would be recorded in the period in which that determination was made.

FERC Complaint Cases

In November 2013, a customer group filed a complaint case with the FERC seeking a reduction in the allowed base return on common equity for the FERC-regulated MISO transmission rate base under the MISO tariff to 9.15%. Currently, the FERC-allowed base return on common equity for MISO transmission owners is 12.38%. In October 2014, the FERC issued an order establishing settlement procedures and, if necessary, hearing procedures regarding the allowed base return on common equity. In January 2015, the settlement judge terminated settlement proceedings and the FERC scheduled the case for hearing proceedings, requiring an initial decision to be issued no later than November 30, 2015. As the original 15-month refund period for the November 2013 complaint case ended in February 2015, another customer complaint case was filed in February 2015. The February 2015 complaint case seeks a reduction in the allowed base return on common equity for the FERC-regulated MISO transmission rate base under the MISO tariff to 8.67%.

In October 2014, the FERC issued an order in a proceeding, in which the Ameren Companies were not involved, reducing the allowed base return on common equity for New England transmission owners from 11.14% to 10.57%, with rate incentives allowed up to 11.74%. The FERC order in the New England transmission owners’ case applied observable market data from October 2012 to March 2013 to determine the allowed base return on common equity. The FERC expects the evidence and the calculation used in the New England transmission owners’ case to guide its decision in the MISO complaint case discussed above. The FERC calculation will establish the allowed base return on common equity, which specifies a unique time period for each complaint case, and will require multiple inputs based on observable market data specific to the utility industry and broader macroeconomic data. In January 2015, the settlement judge for the MISO complaint case ordered that July 13, 2015, should be the cut-off date for the observable market data to be used in the calculation of the allowed base return on common equity. Based on the information in these orders, Ameren and Ameren Illinois recorded current liabilities representing their estimate of the required refunds from the refund effective date of November 12, 2013, through December 31, 2014. Ameren Missouri did not record a liability as of December 31, 2014, and does not expect that a reduction in the FERC-allowed base return on common equity for MISO transmission owners would be material to its results of operations, financial position, or liquidity.

In November 2014, we filed a request with the FERC to include an incentive adder of up to 50 basis points on the allowed base return on common equity for participation in an RTO, and we sought authorization to defer collection of it until after the issuance of the final order addressing the initial MISO complaint case discussed above. FERC approved the request to implement the incentive adder prospectively from January 6, 2015, and to defer collection of it until the issuance of the final order addressing the initial MISO complaint case.

Ameren Missouri Power Purchase Agreement with Entergy

Beginning in 2005, the FERC issued a series of orders addressing a complaint filed in 2001 by the Louisiana Public Service Commission against Entergy and certain of its affiliates. The complaint alleged unjust and unreasonable cost allocations. As a result of the FERC orders, Entergy began billing Ameren Missouri in 2007 for additional charges under a 165-megawatt power purchase agreement that expired August 31, 2009. In May 2012, the FERC issued an order stating that Entergy should not have included additional charges to Ameren Missouri under the power purchase agreement. Pursuant to the order, in June 2012, Entergy paid Ameren Missouri $31 million, with $24 million recorded as a reduction to “Operating Expenses – Purchased power” expense and $5 million for interest recorded as “Miscellaneous income” in the statement of income. The remaining $2 million was recorded as an offset to the FAC under-recovered regulatory asset for the amount refundable to customers. The amount of the Entergy refund recorded to the FAC regulatory asset related to the period when the FAC was effective; therefore, such costs were previously included in customer rates. In November 2013, Entergy filed an appeal of the FERC's May 2012 order with the United States Court of Appeals for the District of Columbia Circuit. Ameren is not able to predict when or how the court will rule on Entergy's appeal.

The Louisiana Public Service Commission appealed the FERC’s orders regarding Louisiana Public Service Commission’s complaint against Entergy Services, Inc. to the United States Court of Appeals for the District of Columbia Circuit. That court ordered further FERC proceedings regarding Louisiana Public Service Commission’s complaint. Ameren Missouri estimates that it could incur an additional expense of up to $8 million if the FERC's May 2012 order is overturned on appeal. Ameren Missouri believes that the likelihood of incurring any expense is not probable, and therefore no liability has been recorded as of December 31, 2014.

Combined Construction and Operating License

In 2008, Ameren Missouri filed an application with the NRC for a COL for a new nuclear unit at Ameren Missouri's existing Callaway County, Missouri, energy center site. In 2009, Ameren Missouri suspended its efforts to build a new nuclear unit at the Callaway site, and the NRC suspended review of the COL application. The suspended status of the COL application currently extends through the end of 2015.

Ameren Missouri estimates the total cost to obtain a COL for the Callaway site to be approximately $100 million. As of December 31, 2014, Ameren Missouri had capitalized investments of $69 million for the development of a new nuclear energy center. Ameren is currently evaluating all potential nuclear technologies in order to maintain an option for nuclear power in the future.

All of Ameren Missouri's capitalized investments for the development of a new nuclear energy center will remain capitalized while management pursues options to maximize the value of its investment. If efforts to license additional nuclear generation are abandoned, the NRC does not extend the COL application suspended status, or if management concludes it is probable that the costs incurred will be disallowed in rates, a charge to earnings would be recognized in the period in which that determination is made.

Regulatory Assets and Liabilities

In accordance with authoritative accounting guidance regarding accounting for the effects of certain types of regulation, we defer certain costs as regulatory assets pursuant to actions of regulators or based on the expected ability to recover such costs in rates charged to customers. We may also defer certain amounts as regulatory liabilities because of actions of regulators or because of the expectation that such amounts will be returned to customers in future rates. The following table presents our regulatory assets and regulatory liabilities at December 31, 2014 and 2013:



	2014						2013
	Ameren Missouri		Ameren Illinois		Ameren			Ameren Missouri		Ameren Illinois		Ameren
Current regulatory assets:
Under-recovered FAC^(a)(b)	$	128	$	—	$	128		$	104	$	—	$	104
Under-recovered Illinois electric power costs^(c)	—		2		2			—		1		1
Under-recovered PGA^(c)	—		20		20			—		1		1
MTM derivative losses^(d)	32		42		74			14		36		50
Energy efficiency riders^(e)	3		—		3			—		—		—
IEIMA revenue requirement reconciliation^(a)(f)	—		65		65			—		—		—
FERC revenue requirement reconciliation^(a)(g)	—		—		3			—		—		—
Total current regulatory assets	$	163	$	129	$	295		$	118	$	38	$	156
Noncurrent regulatory assets:
Pension and postretirement benefit costs^(h)	$	148	$	275	$	423		$	44	$	140	$	184
Income taxes⁽ⁱ⁾	253		3		256			230		7		237
Asset retirement obligations^(j)	—		5		5			—		5		5
Callaway costs^(a)(k)	36		—		36			40		—		40
Unamortized loss on reacquired debt^(a)(l)	72		80		152			77		74		151
Contaminated facilities costs^(m)	—		251		251			—		271		271
MTM derivative losses^(d)	14		144		158			8		118		126
Storm costs⁽ⁿ⁾	—		3		3			5		3		8
Demand-side costs before the MEEIA implementation^(a)(o)	44		—		44			58		—		58
Workers’ compensation claims^(p)	7		7		14			6		6		12
Credit facilities fees^(q)	5		—		5			5		—		5
Common stock issuance costs^(r)	2		—		2			4		—		4
Construction accounting for pollution control equipment^(a)(s)	21		—		21			22		—		22
Solar rebate program^(a)(t)	88		—		88			27		—		27
IEIMA revenue requirement reconciliation^(a)(f)	—		101		101			—		65		65
FERC revenue requirement reconciliation^(a)(g)	—		8		12			—		—		5
Other^(u)	5		6		11			8		12		20
Total noncurrent regulatory assets	$	695	$	883	$	1,582		$	534	$	701	$	1,240
Current regulatory liabilities:
Over-recovered FAC^(b)	$	—	$	—	$	—		$	26	$	—	$	26
Over-recovered Illinois electric power costs^(c)	—		26		26			—		51		51
Over-recovered PGA^(c)	2		25		27			5		29		34
MTM derivative gains^(d)	16		1		17			26		1		27
Wholesale distribution refund^(v)	—		—		—			—		13		13
IEIMA revenue requirement reconciliation^(f)	—		—		—			—		65		65
FERC revenue requirement reconciliation^(g)	—		11		11			—		—		—
Refund reserves for FERC orders and audit findings^(w)	—		21		25			—		—		—
Total current regulatory liabilities	$	18	$	84	$	106		$	57	$	159	$	216
Noncurrent regulatory liabilities:
Income taxes^(x)	$	41	$	14	$	55		$	37	$	3	$	40
Uncertain tax positions tracker^(y)	7		—		7			1		—		1
Removal costs^(z)	886		643		1,529			828		610		1,438
Asset retirement obligation^(j)	182		—		182			146		—		146
Bad debt riders^(aa)	—		7		7			—		8		8
Pension and postretirement benefit costs tracker^(ab)	24		—		24			15		—		15
Energy efficiency riders^(e)	—		39		39			3		33		36
FERC revenue requirement reconciliation^(g)	—		—		—			—		10		10
Other^(ac)	7		—		7			11		—		11
Total noncurrent regulatory liabilities	$	1,147	$	703	$	1,850		$	1,041	$	664	$	1,705


(a)	These assets earn a return.


(b)	Under-recovered or over-recovered fuel costs to be recovered through the FAC. Specific accumulation periods aggregate the under-recovered or over-recovered costs over four months, any related adjustments that occur over the following four months, and the recovery from customers that occurs over the next eight months.


(c)	Costs under- or over-recovered from utility customers. Amounts will be recovered from, or refunded to, customers within one year of the deferral.


(d)	Deferral of commodity-related derivative MTM losses or gains. See Note 7 – Derivative Financial Instruments for additional information.

(e)

The Ameren Missouri balance relates to the MEEIA. Beginning in January 2014, a MEEIA rider allowed Ameren Missouri to collect from or refund to customers any annual difference in the actual amounts incurred and the amounts collected from customers for the MEEIA program costs and its lost revenues. Under the MEEIA rider, collections from or refunds to customers occur one year after the program costs and lost revenues are incurred. The Ameren Illinois balance relates to a regulatory tracking mechanism to recover its electric and natural gas costs associated with developing, implementing, and evaluating customer energy efficiency and demand response programs. Any under-recovery or over-recovery will be collected from or refunded to customers over the 12 months following the plan year.


(f)	The difference between Ameren Illinois' annual revenue requirement calculated under the IEIMA's performance-based formula ratemaking framework and the revenue requirement included in customer rates for that year. Subject to ICC approval, these amounts will be collected from or refunded to customers within two years.


(g)	Ameren Illinois' and ATXI's annual revenue requirement reconciliation adjustments calculated pursuant to the FERC's electric transmission formula ratemaking framework. The under-recovery or over-recovery will be recovered from or refunded to customers within two years.


(h)	These costs are being amortized in proportion to the recognition of prior service costs (credits) and actuarial losses (gains) attributable to Ameren’s pension plan and postretirement benefit plans. See Note 11 – Retirement Benefits for additional information.


(i)	Offset to certain deferred tax liabilities for expected recovery of future income taxes when paid. This will be recovered over the expected life of the related assets.


(j)	Recoverable or refundable removal costs for AROs, including net realized and unrealized gains and losses related to the nuclear decommissioning trust fund investments. See Note 1 – Summary of Significant Accounting Policies – Asset Retirement Obligations.


(k)	Ameren Missouri’s Callaway energy center operations and maintenance expenses, property taxes, and carrying costs incurred between the plant in-service date and the date the plant was reflected in rates. These costs are being amortized over the remaining life of the energy center's current operating license, which expires in 2024.


(l)	Losses related to reacquired debt. These amounts are being amortized over the lives of the related new debt issuances or the original lives of the old debt issuances if no new debt was issued.


(m)	The recoverable portion of accrued environmental site liabilities that will be collected from electric and natural gas customers through ICC-approved cost recovery riders. The period of recovery will depend on the timing of remediation expenditures. See Note 15 – Commitments and Contingencies for additional information.


(n)	Ameren Missouri's actual storm costs that exceed the normalized storm costs for rate purposes. As approved by the December 2012 MoPSC electric rate order, the 2006, 2007, and 2008 storm costs were amortized through December 2014. The Ameren Illinois balance includes 2013 storm costs deferred in accordance with the IEIMA. These costs are being amortized over a five-year period beginning in 2013.

(o)

Demand-side costs incurred prior to implementation of the MEEIA in 2013, including the costs of developing, implementing and evaluating customer energy efficiency and demand response programs. Costs incurred from May 2008 through September 2008 are being amortized over a 10-year period that began in March 2009. Costs incurred from October 2008 through December 2009 are being amortized over a six-year period that began in July 2010. Costs incurred from January 2010 through February 2011 are being amortized over a six-year period that began in August 2011. Costs incurred from March 2011 through July 2012 are being amortized over a six-year period that began in January 2013.The amortization period for costs incurred from August 2012 through December 2012 will be determined in the July 2014 electric rate case.


(p)	The period of recovery will depend on the timing of actual expenditures.


(q)	Ameren Missouri’s costs incurred to enter into and maintain the 2012 Missouri Credit Agreement. Additional costs were incurred in December 2014 to amend and restate the 2012 Missouri Credit Agreement. These costs are being amortized over the life of the credit facility, ending in December 2019, to construction work in progress, which will be depreciated when assets are placed into service.


(r)	The MoPSC’s May 2010 electric rate order allowed Ameren Missouri to recover its portion of Ameren’s September 2009 common stock issuance costs. These costs are being amortized over five years, beginning in July 2010.


(s)	The MoPSC’s May 2010 electric rate order allowed Ameren Missouri to record an allowance for funds used during construction for pollution control equipment at its Sioux energy center until the cost of that equipment was included in customer rates. These costs will be amortized over the expected life of the Sioux energy center, which is currently through 2033.


(t)	Costs associated with Ameren Missouri's solar rebate program beginning in August 2012 to fulfill its renewable energy portfolio requirement. The amortization period for these costs will be three years, commencing with the effectiveness of Ameren Missouri's current July 2014 electric rate case.

(u)

The Ameren Illinois balance includes Ameren Illinois Merger integration and optimization costs, which are being amortized over four years, beginning in January 2012. The Ameren Illinois total also includes costs related to the 2013 natural gas delivery service rate case costs, which are being amortized over a two-year period that began in January 2014. At Ameren Missouri, the balance primarily includes the cost of renewable energy credits to fulfill its renewable energy portfolio requirement. Costs incurred from January 2010 through July 2012 are being amortized over three years, beginning in January 2013.


(v)	Estimated refund to wholesale electric customers as of December 31, 2013. See 2011 Wholesale Distribution Rate Case above.


(w)	Estimated refunds to transmission customers related to FERC orders and audit findings. In regards to the FERC orders, see Ameren Illinois Electric Transmission Rate Refund and FERC Complaint Cases above.


(x)	Unamortized portion of investment tax credits and federal excess deferred taxes. The unamortized portion of investment tax credits and the federal excess deferred taxes are being amortized over the expected life of the underlying assets.


(y)	The tracker is amortized over three years, beginning from the date the amounts are included in rates. See Note 13 - Income Taxes for additional information.


(z)	Estimated funds collected for the eventual dismantling and removal of plant from service, net of salvage value, upon retirement related to our rate-regulated operations.

(aa)

A regulatory tracking mechanism for the difference between the level of bad debt incurred by Ameren Illinois under GAAP and the level of such costs included in electric and natural gas rates. The over-recovery relating to 2012 was refunded to customers from June 2013 through May 2014. The over-recovery relating to 2013 is being refunded to customers from June 2014 through May 2015. The over-recovery relating to 2014 will be refunded to customers from June 2015 through May 2016.

(ab)

A regulatory tracking mechanism for the difference between the level of pension and postretirement benefit costs incurred by Ameren Missouri under GAAP and the level of such costs built into rates. For periods prior to August 2012, the MoPSC's December 2012 electric rate order directed the amortization to occur over five years, beginning in January 2013. For periods after August 2012, the amortization period will be determined in the July 2014 electric rate case.

(ac)

Balance includes the costs of renewable energy credits to fulfill Ameren Missouri's renewable energy portfolio requirement from August 2012 through December 2013, which were less than the amount included in rates. The balance also includes a regulatory tracking mechanism at Ameren Missouri for the difference between the level of storm costs incurred in a particular year and the level of such costs built into rates. The amortization periods for these over-recoveries will be determined in the July 2014 electric rate case.

Ameren, Ameren Missouri, and Ameren Illinois continually assess the recoverability of their regulatory assets. Under current accounting standards, regulatory assets are charged to earnings when it is no longer probable that such amounts will be recovered through future revenues. To the extent that payments of regulatory liabilities are no longer probable, the amounts are credited to earnings.