Per the Comptroller of Maryland, here is more information on when a non-resident does and does not need to file a non-resident return:
If you are a nonresident of Maryland, you are required to file Form 505 (Maryland Nonresident Income Tax Return) and Form 505NR (Maryland Nonresident Income Tax Calculation) if you have income derived from:
- Tangible property, real or personal, permanently located in Maryland;
- A business, trade, profession or occupation carried on in Maryland; or,
- Gambling winnings derived from Maryland sources.
You are not required to file as a nonresident if:
- Your Maryland gross income is less than the minimum filing level for your filing status;
- You had no income from a Maryland source; or
- You reside in Pennsylvania, Virginia, West Virginia or Washington, D.C., and earned only wages in Maryland. For more information, see If You Are A Nonresident Working In Maryland (below) and the instructions in the Maryland nonresident tax booklet.
http://taxes.marylandtaxes.gov/Individual_Taxes/Individual_Tax_Types/Income_Tax/Filing_Information/D...
And, yes, if you are working for an employer who is headquartered in another state, you do not have to file a non-resident return for that state:
https://ttlc.intuit.com/replies/4776808
[Edited 4/6/18|2:37pm]
