State tax filing

1. If I earned an annual one-time bonus payment after I moved to MD (but before 9/13), should I somehow split this to record a part of this as MA Income while Resident (to represent the time I worked in MA to receive this bonus) or should this rather entirely count toward MA Income while Non-Resident as I was in MD when I received this payment?   You should allocate according to your residence when you earned it.  So total bonus payment divided by number of payperiods and then multiply the result by the number of payperiods in MA to get that allocation.  The rest is MD income.   

My wife worked for an MD university for 2021 (remotely during her time in MA until 7/9) and as such her W-2 only states MD state wages and income tax withholding for boxes 15 - 17.

2. Would her MD-withheld income during her residency in MA (1/1 - 7/9) count as MA Income While Resident or should this be 0?  This income is MA resident income during the MA residency period.  

3. Should our non-Maryland income include the portion of her income recorded for #2 (MA Income While Resident)? Yes.  MD does not tax non-residents working remotely out of MD.  

4. Would there be any Credit for Taxes Paid to Another State that should be recorded either for MA or MD State Filing given she withheld MD taxes but is counting her income toward MA taxes in #2?  No, the amount withheld by MD will be credited as a payment toward your MD tax liability and the income will not be allocated to MD.  So no double taxation.   Since there was nothing withheld by MA on that income, your liability there will increase.

5. In general, I am so far incurring a much larger MD state tax due vs. the aggregate tax refund from MA & DC despite having withheld ~4.8% of state tax for MA and ~6.8% of state tax for DC in my W-2 (net of DC refund, with minimal tax dues for MA, I have 2%+ of my annual income currently additionally due for MD state taxes). I am confused as to why this is the case as all three states roughly have similar state income tax rate (5-6%) with slightly higher tax rates for DC and certainly not the full 2% difference between MA and MD state tax rates for my income bracket. What would be the way to best double check my filing and tax amounts to ensure I am not over-paying state taxes?

Once all entries are made you can see a tax summary of each state return with these steps:

1. "Tax Tools" in the left hand menu
2. "Tools"
3. "View Tax Summary" in the main screen
4. "XX State Tax Summary" in the left hand menu

There you can see the taxable income and compare to the tax brackets in your states.  Below are links to MD, MA, DC tax brackets.

MD tax brackets

MA tax brackets

DC tax brackets