I filed Form 8606 in my 2013 tax return even though I didn't have a nondeductible IRA (I had a Roth IRA). How do I correct this mistake? I now have to do a conversion from a traditional IRA to a Roth IRA and I don't want this counted in the total basis on Form 8606.
To correct a mistake in a past year of US federal taxes (or earlier this year), file a corrected return for that year, using Form 1040X.
This may affect your state or city returns for that year too,; check with the appropriate agencies to get their instructions.