If I amended my taxes and now owe them. How long before I have to pay them back?

[xmasbaby0]

What tax year did you amend?   An amended return needs to be filed by mail now, so you can enclose a check or money order with the mailed return.  

[rjs]

If you amended your 2021 tax return, and you owe tax, the payment was due by April 18, 2022. In other words, you're already late because you should have paid the correct full amount of tax that you owed when you filed your original tax return. Pay as soon as you can. You might later get a bill from the IRS for interest and penalties for late payment.