Annuity Investors Life Insurance Company^®

Annuity Investors^® Variable Account C

Flex(b)^®

Individual Flexible Premium Deferred Variable Annuities

Supplement Dated January 24, 2020

to Prospectus Dated May 1, 2019

This supplement is intended to update certain information in the prospectus for the variable annuity you own. All other provisions outlined in your prospectus, as supplemented, remain unchanged. Unless otherwise indicated, terms used in this supplement have the same meaning as in your contract prospectus.

The following replaces the “DEATH BENEFIT” section starting on page 22 of the Prospectus:

DEATH BENEFIT

Definitions

Death Benefit Commencement Date. The first day of the first payment interval for a Death Benefit that is paid as periodic payments or the date of payment for a Death Benefit that is paid as a lump sum. The Beneficiary designates the Death Benefit Commencement Date when filing a claim by Written Request. It can be no earlier than the date that we have received at our administrative office both Due Proof of Death and a claim in Good Order with instructions as to the form of the Death Benefit.

Death Benefit Valuation Date. The earlier of: (1) the date that we have received at our administrative office both Due Proof of Death and a Written Request with instructions as to the form of the Death Benefit; or (2) the first anniversary of death.

Due Proof of Death. A certified copy of a death certificate or a certified copy of a decree made by a court of competent jurisdiction as to the finding of death. We will also accept other proof that is satisfactory to us.

Death Benefit

A Death Benefit is payable under your Contract if, before the Annuity Commencement Date and before the Contract is surrendered:

• an Owner dies; or

• an Owner is a non-natural person and the Annuitant dies.

For this purpose, a trustee is considered to be a non-natural person, and the death of an individual who owns the Contact as a trustee will not be treated as the death of an Owner.

No Death Benefit will be paid until we receive Due Proof of Death. Only one Death Benefit will be paid under the Contract. If a Death Benefit becomes payable, it will be in lieu of all other benefits under the Contract and all other rights under this Contract will be terminated. If your surviving spouse (or your civil union partner/domestic partner in applicable states) becomes a successor owner of the Contract, no Death Benefit will be paid on your death.

Death Benefit under the Standard Contract. The Death Benefit will be based on the greater of:

• the Account Value on the Death Benefit Valuation Date; or

• the Return of Premium Value as described below.

On the Death Benefit Valuation Date, if the Return of Premium Value exceeds the Account Value, then we will add that excess to the Account Value. Any such addition shall be allocated proportionally among the Subaccounts and the Fixed Accumulation Account options based on the values of each such option as of the end of the Valuation Period immediately before that date.

Enhanced Death Benefit Rider. We offer an enhanced Death Benefit through an optional rider to the Contract. To select this Rider, you must make a Written Request. We must receive your Written Request before the Contract effective date.

You may not select this Rider if you or the eldest Owner will be age 80 or older on the Contract effective date. You may not voluntarily terminate this Rider after the Contract effective date.

If you select this Rider, we will increase the annual mortality and expense risk charge applicable to your Contract. The 0.25% increase will compensate us for the additional mortality and expense risk that we assume under the Rider. (For Contracts issued with the Enhanced Death Benefit Rider before May 1, 2009, we increased the annual mortality and expense risk charge by 0.20%.)

If you select this Rider, the amount of the Death Benefit will be based on the greatest of:

• the Account Value on the Death Benefit Valuation Date;

• the Return of Premium Value; or

• the Historic High Value as described below.

On the Death Benefit Valuation Date, if the greater of (1) the Return of Premium Value, or (2) the Historic High Value, exceeds the Account Value, then we will add such excess to the Account Value. Any such addition shall be allocated proportionally among the Subaccounts and the Fixed Accumulation Account options based on the values of each such option as of the end of the Valuation Period immediately before that date.

Return of Premium Value. The Return of Premium Value is the total of all Purchase Payments received by us, reduced proportionally for any withdrawals, including withdrawals to pay charges. Any reduction in total Purchase Payments to reflect withdrawals will be made in the same percentage as the percentage reduction in your Account Value on the date of withdrawal. As a result, this reduction may be greater than the amount of the withdrawal. An example of how a withdrawal impacts the Death Benefit is provided in Appendix C.

Historic High Value. The Historic High Value after the first Contract Anniversary is your largest Account Value on any Contract Anniversary that is before the Death Benefit Valuation Date and before the 80th birthday of the eldest Owner (“largest account value”), reduced by an amount proportionate to any reduction in the Account Value due to a withdrawal after this “largest account value” was reached and any related early withdrawal charge or other related fees or charges. Any reduction in the largest account value to reflect withdrawals will be made in the same percentage as the percentage reduction in your Account Value on the date of withdrawal. As a result, this reduction may be greater than the amount of the withdrawal. An example of how a withdrawal impacts the Death Benefit is provided in Appendix C.

There is no Historic High Value before the first Contract Anniversary. The Death Benefit under this Rider before the first Contract Anniversary is effectively the same as the Death Benefit under the standard Contract.

Other Information about the Death Benefit Amount.

• Unless transferred by the Beneficiary, the portion of the Death Benefit amount allocated to the Subaccounts will remain in those Subaccounts until the Death Benefit Commencement Date.

• The Death Benefit amount under this Contract will be finally determined using the Account Value on the Death Benefit Commencement Date. If the Death Benefit Commencement Date is later than the Death Benefit Valuation Date, the Death Benefit amount may be lower than the amount calculated on the Death Benefit Valuation Date.

• The Death Benefit under this Contract will be reduced by any fees and charges due under this Contract, by any applicable premium tax or other taxes not previously deducted, and by the outstanding balance of any loans.

• We will accrue interest on the Death Benefit payable under the Rider as required by law. Any interest will be added to the Death Benefit to be paid.

Transfers of Death Benefit Amount. Between the Death Benefit Valuation Date and the Death Benefit Commencement Date, the Beneficiary may transfer funds among the Subaccounts and the Fixed Accumulation Account. These transfers are subject to the limitations described in the Transfers section and Appendix B of this prospectus.

Form of Death Benefit Payments. You may elect to have Death Benefit payments made in one lump sum or pursuant to any form of settlement option that is currently available. The standard forms of settlement options are described in the Settlement Options section of this prospectus. There is no additional charge associated with this election.

The election must be made before your death. You may change the election at any time before your death. The election or any change in the election must be made by Written Request.

If you do not make any election, the Beneficiary may make that election after your death and on or before the Death Benefit Commencement Date. A Beneficiary may change the Beneficiary’s own election by Written Request at least 30 days before the Death Benefit Commencement Date.

Lump Sum Payment of Death Benefit prior to January 1, 2012. Prior to January 1, 2012, if the beneficiary was an individual and the lump sum payment option was selected, we may have paid the death benefit by establishing an interest-bearing draft account for the beneficiary in the amount of the death benefit. This account is called the Great American Benefit Choice Account. We sent the beneficiary a personalized “checkbook” for this account. If the beneficiary has not closed this account, then the beneficiary may withdraw all or part of the money in this account at any time by writing a draft against the account. The servicing bank will process the draft by drawing funds from our general account.

The Great American Benefit Choice Account earns interest, which is compounded daily and credited monthly. We set the interest rate for this account. We review the rate periodically and we may change it at any time. We may make a profit on the money held in this account.

The Great American Benefit Choice Account is part of our general account. It is not a bank account, and it is not insured by the FDIC, NCUSIF, or any government agency. As part of our general account, it is subject to the claims of our creditors.

Application of a Death Benefit to a Settlement Option. When a Death Benefit is applied to a settlement option, we promise to pay a stream of benefit payments for the duration of the settlement option selected. Benefit payments are based on the Account Value on the Death Benefit Commencement Date.

The Beneficiary generally will be the person on whose life any Death Benefit payments under a settlement option will be based. If the Beneficiary is a non-natural person, the Beneficiary may elect to have payments under a life option based on the life of a person to whom the Beneficiary is obligated. This election must be made by Written Request before the Death Benefit Commencement Date. Otherwise, a Beneficiary that is a non-natural person may only elect to have settlement option payments made under a fixed period payment option.

Death Benefit Distribution Rules. Any designation of the Death Benefit Commencement Date, any election of the form of death benefit payments, and any change in the designation or the election is subject to the Death Benefit Distribution Rules provision of the Contract. These rules are summarized below.

• For a Tax Qualified Contract. Death Benefit payments must meet the required minimum distribution rules set out in the tax qualification endorsement.

• For any other Contract. The Death Benefit must be paid either: (1) in full within 5 years of death; or (2) over the life of the Beneficiary or over a period certain not exceeding the Beneficiary’s life expectancy, with payments at least annually starting within one year of death.

The following replaces the first paragraph of the subsection entitled “Form of Benefit Payments under Settlement Options” of the “SETTLEMENT OPTIONS” section on page 24 of the Prospectus:

Benefit payments may be calculated and paid as fixed dollar payments, variable dollar payments, or a combination of both. We guarantee only the amount of fixed dollar payments. The Beneficiary (or the applicable payee) bears the risk that any variable dollar payment may be less than the initial variable dollar payment, or that it may decline to zero, if Benefit Unit Values for that payment decrease sufficiently.

The following replaces the subsection entitled “Successor Owner” of the “Ownership Provisions” subsection of the “THE CONTRACT” section on page 26 of the Prospectus:

Successor Owner. In some cases, your spouse (or your civil union partner/domestic partner in applicable states) may succeed to the ownership of the Contract after your death. Specifically, if a Death Benefit is payable on account of your death and your spouse (or your civil union partner/domestic partner) is the sole Beneficiary under the Contract, he or she will become the successor owner of the Contract if: (1) you make that Written Request before your death; or (2) after your death, your spouse (or your civil union partner/domestic partner) makes that Written Request before the

Death Benefit Commencement Date. A successor owner will succeed to all rights of ownership under the Contract except the right to name another successor owner.

As required by federal tax law, the Contract contains rules about the rate at which a death benefit must be paid to a beneficiary who is not your spouse. If the successor owner is not your spouse as defined by federal tax law, then after your death the contract values must be distributed in a manner that complies with these rules.

Step Up in Account Value for Successor Owner. If your spouse (or your civil union partner/domestic partner in applicable states) becomes the successor owner of the Contract, the Account Value may be increased. There is no additional charge associated with this feature. Any such increase will be equal to the amount, if any, that the Account Value would have been increased on the Death Benefit Valuation Date if your spouse (or civil union partner/domestic partner) had elected to take the Death Benefit. An increase will only apply if the Death Benefit would have been based on the Return of Premium Value or Historic High Value.

For this purpose, the Death Benefit Valuation Date is the earlier of: (1) the date that we have received at our administrative office both Due Proof of Death and a Written Request to become successor owner of the Contract; or (2) the first anniversary of death. Any such increase shall be effective on the Death Benefit Valuation Date, and shall be allocated proportionally among the Subaccounts and the Fixed Accumulation Account options based on the value of each such option as of the end of the Valuation Period immediately before that date.

The following replaces the “ABANDONED PROPERTY AND ESCHEATMENT” section on page 28 of the Prospectus:

Every state has unclaimed property laws. These laws generally declare annuity contracts to be abandoned after a period of inactivity of three to five years (1) from the first day of the period during which annuity benefit payments are to be paid; or (2) from the date of death for which a death benefit is due and payable. For example, if the payment of a death benefit has been triggered, but the Beneficiary does not come forward to claim the death benefit in a timely manner, the unclaimed property laws will apply.

If a death benefit, annuity benefit payments, or other Contract proceeds are unclaimed, we will pay them to the abandoned property division or unclaimed property office of the applicable state. (Escheatment is the formal, legal name for this process.) For example, on an unclaimed death benefit, depending on the circumstances, the proceeds are paid (1) to the state where the Beneficiary last resided, as shown on our books and records; (2) to the state where the Owner last resided, as shown on our books and records; or (3) to Ohio, which is our state of domicile. The state will hold the proceeds without interest until a valid claim is made by the person entitled to the proceeds.

If the Contract owner dies and we are unable to locate the beneficiary, or if the Contract requires annuity benefit payments to start and we cannot locate the owner, the Account Value of the Contract will remain in the Subaccount and Fixed Accumulation Account options until the death benefits or Contract proceeds are claimed or escheated. If escheated, the death benefit amount or Contract proceeds will be finally determined using the Account Value at the end of the Valuation Period that is no more than seven days before date that we make the escheat payment to the state.

To prevent escheatment of the death benefit, annuity benefit payments or other proceeds from your annuity, it is important:

• to update your contact information, such as your address, phone number and email address, if and as it changes; and

• to update your Beneficiary and other designations, including complete names, complete addresses, phone numbers, and social security numbers, if and as they change.

Please contact us at P.O. Box 5423, Cincinnati, OH 45201-5423, or call us at 1-800-789-6771, to make such changes.

State unclaimed property laws do not apply to annuity contracts that are held under an employer retirement plan that is subject to the Employee Retirement Income Security Act of 1974 (ERISA).

Please retain this supplement for future reference.