The Government has produced a “Z clause” for use with NEC3 contracts, as part of its initiative to make its fair payment provisions a contractual requirement in all central government construction contracts. The Government Information Note 1/2011 defines the payment periods for Tiers 1, 2 and 3 in the supply chain as, respectively, 14, 19 and 23 calendar days from the Due Date.

The Note also says that the Construction Clients Board has agreed that central government departments, their agencies and non-departmental public bodies should adopt Project Bank Accounts in line with Government guidance, unless there are compelling reasons not to do so.

See: http://www.cabinetoffice.gov.uk/resource-library/fair-payment-construction