Contact the payer and ask for a corrected
Form 1099-R. The IRS receives all
Form 1099-Rs from the payers. So if the amount you report on your tax return doesn't match the amount the IRS received from the payer, the IRS may make an adjustment to your tax return or send you a notice asking about the difference.
However, if the amount on the
Form 1099-R is less than what it should be, then there's not a problem in going ahead and entering the correct amount of income on your tax return. The IRS will not send you a notice asking why you are reporting more income than the
Form 1099-R income.
For example, if your
Form 1099-R is for $200 of income, but you enter the correct amount of $250, the IRS won't care that you reported more income than they were expecting. However, if the correct amount is $100 and you enter $100 but the
Form 1099-R is for $200, then the IRS would want to know why you aren't reporting the $200 on your tax return.
If the payer won't give you a corrected
Form 1099-R in a timely manner, it gets more complicated. You can fill out IRS
Form 4852 then choose to mail your tax return instead of e-filing it, and include the
Form 4852 as part of your tax return.