Maryland allows online direct filing of form 502, so my plan is to use TurboTax Online to file Federal, California, and MD form 505, and then separately file 502 electronically via the Maryland portal. I'll have to fill both 505 and 502 first prior to filing California in order to compute the tax credit in CA earned for MD taxes paid. One concern is that I believe CA requires filing a copy of the other state tax return when claiming the credit, and I will have no way to electronically attach both forms 505 and 502 to my CA return.
