Which notices do I owe my subcontractors each month?

The exact regime lives in each subcontract, the first thing to check, because amended forms move the windows and the statutory defaults only apply where the paperwork is silent. The standard shape under the Construction Act: each cycle you must serve a Payment Notice stating the sum you consider due and its basis, and, if you later intend to pay less, a Pay Less Notice by its own, later deadline, again stating the sum and its basis. Two failures dominate. First, silence: no Payment Notice, no Pay Less Notice, and the subcontractor's application becomes the Notified Sum, payable in full by the Final Date For Payment, however optimistic its arithmetic, and an adjudicator will enforce that without examining the merits. Second, the notice that exists but does not work: served outside its window, or in a covering email that never states a basis, or netting off a contra-charge no paperwork supports. It fails exactly when it is needed. The discipline that avoids both is unexciting: one calendar of every account's windows, each notice drafted before its date in the required form, reasons stated so they could be read out loud, service by the route the subcontract demands, and proof kept. Main contractors who run that discipline stop paying for other people's arithmetic; the ones who do not are, sooner or later, made to.

Take a main contractor with eight subcontractors, whose notices are whatever the surveyor manages between site visits. One month the steelwork subcontractor's application arrives carrying a remeasure the site never agreed. Everyone knows it is wrong; nobody serves anything inside the windows, because knowing felt like enough. The subcontractor adjudicates on the Notified Sum and wins without the merits ever being examined: the money goes out, right or wrong, because the paperwork that could have disagreed was never served. The month after, the regime changes: every subcontract's windows on one calendar, a Payment Notice drafted against each application with the assessment attached, Pay Less Notices with their grounds where deductions are real, everything signed and served on its date with proof kept. The next inflated application meets a notice stating a lower sum and showing its workings, and the argument that follows happens on the merits, inside the account, not in an adjudication already lost on procedure.