Massachusetts General Laws Part I. Administration of the Government (Ch. 1-182) Ch. 83, § 15C

Notwithstanding any general or special law to the contrary, a city or town that accepts this section may assess and collect interest on an unpaid balance of a sewer betterment assessment at a rate up to 2 per cent above the net rate of interest chargeable to the city or town for the project to which the assessment relates.