When can you issue a Pay Less Notice?

In the window between the sum it responds to coming into existence and the prescribed period before the Final Date For Payment, the last day the money can lawfully arrive; where the contract is silent, the Scheme for Construction Contracts makes that 7 days. A Pay Less Notice has to answer something: fired off before the application or Payment Notice it responds to exists, it risks being treated as answering nothing, and served after the prescribed period it counts for nothing. Inside the window, later is better informed, because the notice states the sum due as at the day of service, but leaving a day or two of margin reduces the risk of an argument about service deciding the whole round against you. The window opens afresh with every Due Date, the date the payment obligation is fixed, so the counting repeats every round on every live contract.

A subcontractor's application is due on the 10th and the Final Date For Payment for that round is the 30th, with a 7 day rule. A Pay Less Notice on the 8th, before the application exists, risks being treated as answering nothing. One on the 25th is too late, inside the final 7 days. The safe window is roughly the 11th to the 23rd; serving near the later end lets the contractor take account of a snag found on the 21st, while stopping a day short leaves margin so an argument about when it arrived cannot swallow the round. Next month, the counting starts again from that month's Due Date.