I performed my backdoor Roth declaration incorrectly on a 2023 amendment and paid lots of taxes. How can I amend this error so that I can get my money back?

To avoid tax on this conversion, you need to file or had already filed a Form 8606 showing a non-deductible contribution.  See Form 8606 Lines 1,2.

OR

If you took a deduction for the traditional IRA contribution, that offsets the tax, so it all balances out and there is no reason to amend.

--

Amend with a properly filled out Form 8606 attached and some or all of your tax on that conversion will be refunded.

NOTE: Generally, if you already had a balance in IRAs before attempting this, you cannot do it  completely tax-free.

@neekycliffe