@mdktech24
The penalty is calculated from whenever you owed to whenever you pay. So if you only pay when you file your return on April 15, 2025, you would owe 12 months on the missed April 15, 2024 payment, 10 months on the missed June payment, and so on.
You should also review the penalty rates at the FTB. My assumption was using IRS rules. It looks like the FTB is a bit more harsh, they will charge you 5% of the missed amount, plus 0.5% per month for every additional month, plus 8% APR on the entire missed amount plus penalties. That would mean your missed April 15, 2024 payment could accrue 11% as a penalty and 8% interest, for a total of approximately $142. Lower amounts for the rest since they were owed shorter amounts of time.
https://www.ftb.ca.gov/pay/penalties-and-interest/index.html
https://www.ftb.ca.gov/pay/penalties-and-interest/interest-and-estimate-penalty-rates.html
For a conversion made at the end of the year, you really should make your payment by January 15, 2025 and then use the annualized income method to compute the penalty, it should almost completely eliminate it.
