The important thing to remember in Maryland is that the rule is not just 50% of the time must be outside of Maryland. You must have more time in another SINGLE state than you do in Maryland. So 4 months in Maryland and then 3 months in VA and 3 months in North Carolina and then 2 months in DC means Maryland will come after you for taxes. The other bogus Maryland deal is that Maryland wants you to pay the tax upfront before you have been in the state for 90 days if you plan to stay for more than 90 days even iof you plan to go elsewhere for more than 4 months in another state. Then there is currently NO FORMAL METHOD to request a refund of your excise tax even if you can prove you are entitled to get it back. This link to MD DNR. Just be careful they play dirty. When I was there a boater took them to court over the wording of their tax law saying the intent was not to tax people who were visiting with no intent to have MD their primary state of residence. The day after he won the legislature modified the tax law to close the loophole so it applies to anyone who boats in MD waters. BTW the Potomac is all in MD up to the Virginia shoreline.