I can help you with the part year return. It is very simple, enter the dates lived in DC... I usually pay them their fair portion of the tax on DC 40. For example, is someone lives from January 1, to May 31, and then went back to his state and came back to DC September 1, and stayed for the rest of the year, I enter the dates to include 8 months in the district and since in this case the other state is far away, I enter the amounts based on the W-2 information. In this case, I would enter the whole amount for DC. DC doesn't have D-40NR
Let's say that you work for the red cross and you lived 8 months in DC and 4 months in another state, I would use this formula to calculate DC fair's portion. I would enter the W-2 income on form 1040. That whole income would be transfer to DC income. On page 2, line 8, income received while non-resident, I would enter the enter =(W-2Income\12*4) and the rest will be done automatically. Provided that you... on data tab, entered the correct dates that will be ONLY 8 months. Same is true for someone who works in VA, lives in the District and in the middle of the year moves to MD keeping the same job. In this case, VA gets 0, MD gets 1/2 of the income and DC gets the other half due to the reciprocity agreements. People here in these three states only pay income taxes where they live.
NT.- About 10 years ago, I sent ATX the formula that they should use to help us not to make a mistake when entering the dates of residency and they didn't fix it. So for example, you have a single person who lived in the district from June 1, 2019 until the end of the year and you by mistake enter from June 1, 2019 until Dec 31, 2020, the program will give you a standard deduction of more than $18,000. By the way, DC follow the new Federal Standard deduction and no personal exemption. And if you enter the date of Dec 31, 2021, you will get a bigger standard deduction and your Earn Income Credit which is 32% of the federal will be almost as big of the federal.
Thank you for reading the previous paragraph which you can eliminate because we, tax preparers, never make a mistake, correct?