Contracts across the Gulf are usually based on the FIDIC Red or Yellow Book. Payment runs on the Interim Payment Certificate: the Engineer certifies within 28 days of the Statement and the Employer pays within 56 days, counted in calendar days. FIDIC has no UK-style payment or pay less notices, so the mechanism is the certificate, not the notice.
Not your whole portfolio. One live job, one certificate. If it does not save you time the first time you use it, walk away and take your data with you.