If a tax offset or math error decreases your IRA contribution, and you've already claimed a deduction on your tax return, then you'll need to do one of the following: Complete the contribution for the intended amount with outside money by the due date of the tax return, or file an amended return without the contribution. You can file an amended return with the contribution amount in the case of a partial deposit. Keep in mind, an increase to your deposit might impact accounts with contribution limits. Be sure to compare the intended deposit amounts from your tax return with actual deposit amounts when you receive your tax refund.