81. Interest

On any debt or sum, payable at a certain time or otherwise, whereon interest is not reserved or agreed for, and which is overdue at the date of the winding up order or resolution, the creditor may prove for interest at a rate not exceeding 6% per annum to that date from the time when the debt or sum was payable, if the debt or sum is payable by virtue of a written instrument at a certain time, and if payable otherwise, then from the time when a demand in writing has been made, giving notice that interest will be claimed from the date of the demand until the time of payment.