Claiming non-traditional IRA catchup contributions to establish the basis
In 2020 I converted a traditional IRA to a Roth IRA which closed the traditional IRA. But then I contributed to a new traditional IRA I had to establish for catchup contributions so I could backdoor those into my Roth through conversion. I lad to leave some $$$ in the new traditional IRA so the account would stay open. These are non-deductible contributions. How do I claim them to establish my basis?
Thank you