Section 50. (a) In the selection of a designer or interior designer when the fee for design services has been set by the commissioner prior to the selection process, the commissioner shall appoint a designer or interior designer from among the list transmitted to the commissioner under section 49. If the commissioner appoints any designer or interior designer other than the 1 ranked first by the board, the commissioner shall file a written justification of the appointment with the board.

(b) When the fee for design services is to be negotiated, the commissioner shall review the list transmitted by the board and may exclude any designer or interior designer from the list if a written explanation of the exclusion is filed with the board. The commissioner shall then appoint a designer or interior designer based on successful fee negotiation. The commissioner or persons designated by the commissioner shall first negotiate with the first ranked designer or interior designer remaining on the list. Should the commissioner be unable to negotiate a satisfactory fee with the first ranked designer or interior designer within 30 days, negotiations shall be terminated and negotiations undertaken with the remaining designers or interior designers, 1 at a time, in the order in which they were ranked by the board, until an agreement is reached. In no event may a fee be negotiated which is higher than a maximum fee set by the commissioner prior to selection of finalists. Should the commissioner be unable to negotiate a satisfactory fee with any designer or interior designer initially selected as a finalist by the board, the board shall recommend additional finalists in accordance with this chapter. The commissioner may require a finalist with whom a fee is being negotiated to submit a fee proposal and include with it such information as the commissioner requires to provide current cost and pricing data on the basis of which the designer's or interior designer's fee proposal may be evaluated.

(c) All fees shall be stated in designer's contracts and in any subsequent amendment thereto as a total dollar amount. Contracts may provide for equitable adjustments in the event of changes in scope or services.

(d) Notwithstanding any general or special law to the contrary, all public entities within the commonwealth, agencies and authorities of the commonwealth and municipal entities within the commonwealth, including departments, boards, committees or commissions shall be entitled to withhold up to 5 per cent of contract fees earned and invoiced as part of professional service contracts, during the life of the contract. Withheld fees shall be held for not longer than 2 invoice periods when the contractor is permitted to invoice monthly, or until successful completion of the next contract phase or stage when the contractor is permitted to invoice by project phase or stage. When the work covered by the contract is completed, all remaining withheld fees shall be paid to the contractor within 2 months from the date of completion. If the withholdings are not paid to the contractor within the stipulated time limit, the amount of the withholding in arrears shall be increased at a 12 per cent annual rate.

(e) Notwithstanding any general or special law to the contrary, agencies and authorities of the commonwealth and municipal entities within the commonwealth, including departments, boards, committees or commissions, shall pay all outstanding withheld fees on professional service contracts, when the withholding has been held for longer than 2 invoice periods for active contracts, or that remains withheld on contracts which have been completed, or for which the work of the contractor has been completed.