The following table presents Ameren’s, Ameren Missouri’s and Ameren Illinois’ regulatory assets and regulatory liabilities at December 31, 2013, and 2012:



	2013						2012
	Ameren Missouri		Ameren Illinois		Ameren			Ameren Missouri		Ameren Illinois		Ameren
Current regulatory assets:
Under-recovered FAC^(a)(b)	$	104	$	—	$	104		$	145	$	—	$	145
Under-recovered Illinois electric power costs^(c)	—		1		1			—		—		—
Under-recovered PGA^(c)	—		1		1			5		7		12
MTM derivative losses^(d)	14		36		50			13		77		90
Total current regulatory assets	$	118	$	38	$	156		$	163	$	84	$	247
Noncurrent regulatory assets:
Pension and postretirement benefit costs^(e)	$	44	$	140	$	184		$	348	$	424	$	772
Income taxes^(f)	230		7		237			231		4		235
Asset retirement obligations^(g)	—		5		5			—		5		5
Callaway costs^(a)(h)	40		—		40			44		—		44
Unamortized loss on reacquired debt^(a)(i)	77		74		151			81		100		181
Recoverable costs – contaminated facilities^(j)	—		271		271			—		248		248
MTM derivative losses^(d)	8		118		126			7		128		135
Storm costs^(k)	5		3		8			9		—		9
Demand-side costs before MEEIA implementation^(a)(l)	58		—		58			73		—		73
Reserve for workers’ compensation liabilities^(m)	6		6		12			6		6		12
Credit facilities fees⁽ⁿ⁾	5		—		5			6		—		6
Common stock issuance costs^(o)	4		—		4			7		—		7
Construction accounting for pollution control equipment^(a)(p)	22		—		22			23		—		23
Solar rebate program^(a)(q)	27		—		27			5		—		5
IEIMA revenue requirement reconciliation^(r)	—		65		65			—		—		—
Other^(s)(t)	8		12		25			12		19		31
Total noncurrent regulatory assets	$	534	$	701	$	1,240		$	852	$	934	$	1,786
Current regulatory liabilities:
Over-recovered FAC^(b)	$	26	$	—	$	26		$	—	$	—	$	—
Over-recovered Illinois electric power costs^(c)	—		51		51			—		58		58
Over-recovered PGA^(c)	5		29		34			—		15		15
MTM derivative gains^(d)	26		1		27			18		1		19
Wholesale distribution refund^(u)	—		13		13			—		8		8
IEIMA revenue requirement reconciliation^(r)	—		65		65			—		—		—
Total current regulatory liabilities	$	57	$	159	$	216		$	18	$	82	$	100
Noncurrent regulatory liabilities:
Income taxes^(v)	$	38	$	3	$	41		$	42	$	4	$	46
Removal costs^(w)	828		610		1,438			766		581		1,347
Asset retirement obligation^(g)	146		—		146			80		—		80
MTM derivative gains^(d)	1		—		1			2		—		2
Bad debt riders^(x)	—		8		8			—		12		12
Pension and postretirement benefit costs tracker^(y)	15		—		15			23		—		23
Energy efficiency riders^(z)	3		33		36			—		20		20
IEIMA revenue requirement reconciliation^(r)	—		—		—			—		55		55
FERC transmission revenue requirement reconciliation^(aa)	—		10		10			—		—		—
Other^(ab)	10		—		10			4		—		4
Total noncurrent regulatory liabilities	$	1,041	$	664	$	1,705		$	917	$	672	$	1,589


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


(f)	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.


(g)	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.


(h)	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.


(i)	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.


(j)	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.

(k)

Actual storm costs in a test year that exceed the MoPSC staff’s normalized storm costs for rate purposes. As approved by the December 2012 MoPSC electric rate order, the 2006, 2007, and 2008 storm costs are being amortized through December 2014. As approved by the May 2010 MoPSC electric rate order, the 2009 storm costs are being amortized through June 2015. The Ameren Illinois total includes 2013 storm costs deferred in accordance with the IEIMA. These costs are being amortized over a five-year period beginning in 2013.

(l)

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.


(m)	Reserve for workers’ compensation claims. The period of recovery will depend on the timing of actual expenditures.


(n)	Ameren Missouri’s costs incurred to enter into and maintain the 2012 Ameren Missouri Credit Agreement. These costs are being amortized over five years, beginning in November 2012. These costs are being amortized to construction work in progress, which will be depreciated when assets are placed into service.


(o)	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.


(p)	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 could be included in customer rates. These costs will be amortized over the expected life of the Sioux energy center, which is currently through 2033.


(q)	Costs associated with Ameren Missouri's solar rebate program beginning in August 2012 to fulfill Ameren Missouri's renewable energy portfolio requirement. The amortization period for these costs will be three years, commencing with the next Ameren Missouri electric rate case order.

(r)

The asset balance relates to the difference between Ameren Illinois' 2013 revenue requirement calculated under the IEIMA's performance-based formula ratemaking framework, and the revenue requirement included in customer rates for 2013. Subject to ICC approval, this asset will be collected from customers in 2015. The liability balance relates to the difference between Ameren Illinois' 2012 revenue requirement calculated under the IEIMA's performance-based formula ratemaking framework and the revenue requirement included in customer rates for 2012. This liability will be refunded to customers in 2014.

(s)

The Ameren Illinois total includes Ameren Illinois Merger integration and optimization costs, which are 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. The Ameren Illinois total also includes a portion of the unamortized debt fair value adjustment recorded upon Ameren's acquisition of IP. This portion is being amortized over the remaining life of the related debt. 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.


(t)	The Ameren total includes $5 million for ATXI's revenue requirement reconciliation adjustments for 2012 and 2013 calculated pursuant to the FERC's electric transmission formula ratemaking framework. These adjustments will be collected from customers in 2014 for the 2012 revenue requirement reconciliation and in 2015 for the 2013 revenue requirement reconciliation.


(u)	Estimated refund to wholesale electric customers. See 2011 Wholesale Distribution Rate Case above.


(v)	Unamortized portion of investment tax credits, federal excess deferred taxes, and uncertain tax position tracker. The tracker is being amortized over three years, beginning in January 2013. The unamortized portion of investment tax credit is being amortized over the expected life of the underlying assets.


(w)	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.

(x)

A regulatory tracking mechanism for the difference between the level of bad debt expense incurred by Ameren Illinois under GAAP and the level of such costs included in electric and natural gas rates. The over-recovery relating to 2011 was refunded to customers from June 2012 through May 2013. The over-recovery relating to 2012 is being refunded to customers from June 2013 through May 2014. The over-recovery relating to 2013 will be refunded to customers from June 2013 through May 2014.

(y)

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 a future Ameren Missouri electric rate case.

(z)

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


(aa)	Ameren Illinois' 2013 revenue requirement reconciliation adjustment calculated pursuant to the FERC's electric transmission formula ratemaking framework. This liability will be refunded to customers in 2015.


(ab)	Balance primarily 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 amortization period for this over-recovery will be determined in a future Ameren Missouri electric rate case.