Generally, you cannot claim a capital gains loss on your retirement accounts that already are receiving favorable tax treatment. The only time you would have a loss is when you receive a distribution that had previously been taxed.

About Publication 575, Pension and Annuity Income

This publication discusses the tax treatment of distributions you receive from pension and annuity plans and also shows you how to report the income on your federal income tax return. How these distributions are taxed depends on whether they are periodic payments (amounts received as an annuity) that are paid at regular intervals over several years or nonperiodic payments (amounts not received as an annuity).