SECTION 4. Collector of taxes; penalties

The board of assessors, upon assessing the excise imposed by this chapter, shall commit the same to the collector of taxes with their warrant for the collection thereof. The collector of taxes shall seasonably notify the owner of the excise assessed and the due date, but failure to receive notice shall not affect the validity of the excise. Said excise shall be due and payable at the expiration of sixty days from the date upon which the notice was issued by the collector pursuant to this chapter.

Failure to pay said excise by the due date shall result in a penalty being imposed which shall be equal to twenty dollars or twenty per cent of the amount of the excise due, whichever is greater. The penalty shall be in addition to the amount of excise due and any interest thereon imposed by law. If said excise remains unpaid after the due date, the harbormaster of a city or town shall refuse to allow the vessel to moor, dock, or otherwise be situated within the waterways of said city or town. All sums received from said penalty shall be credited to the Municipal Waterways Improvement and Maintenance Fund, established under the provisions of clause (72) of section five of chapter forty.