Section 29. Any subsidiary account set up as prescribed in a schedule referred to in section 27, on the books of any department, office, commission or institution, receiving an appropriation from the commonwealth, may be increased or decreased by the interchange with any other such subsidiary account within the same appropriation account by the officer in charge of such department, office, commission or institution upon his certification to the budget director that such interchange is required to incur obligations to meet statutory responsibilities under general or special law where funds are otherwise not available, unless otherwise provided by general or special act. For any certification requesting a transfer to a subsidiary account that has not been established within a schedule prescribed under said section 27, the officer shall include the reasons for the new subsidiary account. Every such certification shall include a statement of the details of the necessity of the transfer and of the probable consequences if said interchange should not be made. An officer making any such certification shall file forthwith a copy thereof within the central accounting system under policies and procedures adopted by the secretary of administration and finance.

The comptroller may accept affidavits that expenditures are in accordance with the purpose of such appropriation or subsidiary accounts and do not exceed the unencumbered balances of the amounts provided therefor. The comptroller shall refuse to permit a disbursement or the incurring of an obligation if funds or allotments of funds under an appropriation account or subsidiary account under an appropriation account, sufficient to cover such disbursement or obligation are not available and shall immediately give notice of such refusal to the department, office, commission or institution proposing the expenditure, and, in the case of a department, office, commission or institution within any of the executive offices established by chapters 6A and 7 to the secretary having charge of such executive office.

The secretary of administration and finance may establish regulations or policies governing the interchange of funds under this section.