A 6D certificate or form is almost always required by Massachusetts real estate regulations for the sale or transfer of ownership of condominium units. 6D certificates primarily ensure that any unpaid condominium fees are resolved before said sale or transfer of ownership. The form indicates that all common charges due as of the date through which payment has been received are resolved. Any remaining fees or charges must be paid in full at least five business days before issuing the 6D certification. In the case of a condominium unit sale, the forms condominium document and other association fees are typically paid for by the seller.