What is the Due Date?

The Due Date is the date on which the obligation to pay for a round of work is fixed under the contract, and the anchor from which every other deadline is measured: the payer's Payment Notice, its statement of the sum due, runs 5 days from it, the Final Date For Payment, the last day the money can lawfully arrive, is set by reference to it, and the Pay Less Notice deadline counts back from that. It is not the day money changes hands, and under the widely used JCT contract forms it is not the same as the Interim Valuation Date, which falls a little earlier and is the point at which the work is priced and applications are expected. Under some contracts a late application can push the Due Date back, dragging the whole round of deadlines with it. Get the Due Date wrong and every later date shifts with it, so pin it down first.

A JCT job has an Interim Valuation Date on the 20th of each month, with the Due Date 7 days later, the 27th, and payment due 14 days after that. The 20th is when the work is priced and the contractor applies; the 27th is the Due Date that starts the clock. From the 27th, the surveyor has 5 days to serve a Payment Notice, reads off the Final Date For Payment as around the 10th of the next month, then counts back for the Pay Less Notice deadline. Treat the 20th as the Due Date and every later date lands a week early, so a Payment Notice served in good faith could turn out days late.