We knew something was wrong by comparing our W-2's (as my company is based in VA too and we float around the same income bracket). We were able to find out by looking up the local tax for the area and multiply it by the amount of income he made while with that company. It was the same amount that he was short for MD state income taxes. For instance, if your husband made 25K in the last 4 months with that company, and you live in St. Mary's ($25000 x .03= $750). Your numbers will vary based on county and the amount, but its definitely not a few dollars.
http://taxes.marylandtaxes.com/Indi...on/Tax_Rates/Local_and_County_Tax_Rates.shtml
Once we figured it out, he then went to his payroll to correct it starting this year, but yes he had to come out of pocket with it for the amount owed from last year. They make it difficult because the W-2 wraps up everything under the "state tax" and doesn't show the breakout for state and local.
Hopefully that helps, message me if you have any questions!