In respect of instruments executed on or after 1 October 1999, interest is chargeable on stamp duty that is not paid within 30 days of execution of a stampable document, wherever execution takes place (SA 1891, s. 15A). Interest is payable on repayments of overpaid duty, calculated from the later of 30 days from the date of execution of the instrument, or lodgement with the Stamp Office of the duty repayable (FA 1999, s. 110). Interest is rounded down (if necessary) to the nearest multiple of £5. No interest is payable if that amount is under £25. The applicable interest rate is as prescribed under FA 1989, s. 178.