from a MD tax expert (not me)

PLEASE SAVE THIS IN YOUR FILES:
The C’s Office is planning to clarify in the instructions —
On Form 511, where do we enter the prior year overpayment applied to 2021?
Last year’s overpayment applied to this year should go on line 13a. Additionally, an electing PTE that filed a 511 last year, but files a 510 this year should add those payments to the 510 line 16a.