If you are doing business on Nantucket, under anything other than your own name, you are required by MGL to file a DBA with the Town Clerk's Office.
There are three exceptions to this MGL. If you are currently incorporated within the State of Massachusetts, hold an LLC with the State of Massachusetts or have a Trademark with the State of Massachusetts then, by law, you are not required to file.
Please remember that filing a DBA is not a name protection unless you fall under the three exceptions.
The filing fee is $40 and your DBA will be valid for four years from the date of filing.