Amend old tax returns

[yatoshura]

I recently hired a pro CPA to check and review all my tax returns since 2015 and they were able to find several years where I overpaid taxes due to some mistakes and miscalculations. Is there any way to amend those returns older than 5 years? If not, will those excess taxes I paid be returned or counted toward a future year tax returns in any way?

[MinhT1]

You cannot amend tax returns more than 3 years old.

This IRS says in this document:

The latest date, by law, you can claim a credit or federal income tax refund for a specific tax year is generally the later of these 2 dates:

• 3 years from the date you filed your federal income tax return, or
• 2 years from the date you paid the tax.

This time period is called the Refund Statute Expiration Date (RSED).

[yatoshura]

So there is no way to use those excess tax payments for any future tax returns? Not even as deductions or credits?

[DaveF1006]

Yes, that is correct. As @MinhT1  says, you can only amend the prior three years returns to claim a refund. Beyond that, the excess tax payments cannot be claimed.