Found the answer: https://www.whitecoatinvestor.com/late-contributions-to-the-backdoor-roth-ira/
Looks like you report taxes for the PREVIOUS year (2022) as if you only made a $6000 traditional IRA contribution. Then in the current tax year (2023), you claim the full $12,000 as a Roth contribution (from the trad-->Roth conversion).
This allows you to invest the max in both years in the event your income goes over the Roth IRA limits and you don't realize til the next year.
Patrick
