Contracts and payment
Interim payment certificates: prepare and review a monthly claim
Published:
What goes into an interim payment application, how retention and advance recovery work, and how to keep cost, certified value and cash apart.
Original guide. It describes common practice; your contract’s payment clauses, forms and deadlines govern. It is not legal advice.
What an interim payment is
Most construction contracts pay the contractor in stages, usually monthly, against the value of work done. The contractor submits an application, the engineer or contract administrator assesses it and certifies an amount, and the employer pays within the period the contract sets.
Under the FIDIC Red Book, for example, the application, the certificate and the payment each have their own sub-clause and time limit in Clause 14. Read the edition and the Particular Conditions of your own contract before relying on any period.
What the application contains
Values are normally cumulative to date, with the previous certificate deducted at the end.
| Line | How it is valued |
|---|---|
| Measured work to date | Quantities measured to date × contract rates. |
| Variations | Instructed changes, valued under the contract’s variation rules. |
| Materials on site | Where the contract allows it, part of the value of materials delivered but not yet built in. |
| Retention | A percentage withheld from each payment and released at completion and after the defects period. |
| Advance payment recovery | Deductions from each certificate that repay any advance. |
| Previous certificates | The cumulative amount already certified, deducted to give this period’s amount. |
Keep cost, certified value and cash apart
Three numbers are easy to confuse: what the work cost, what has been certified and what has been paid. A project can be certified ahead of cost and still be short of cash, or the reverse. Track all three every month, and explain each gap in a sentence.
Our synthetic example walks through the arithmetic with invented figures.
Review before you submit
A short checklist catches most rejected items:
- Every quantity has measurement evidence: a survey, a drawing mark-up or an inspection record.
- Every variation claimed has an instruction or a notice behind it.
- Retention and advance recovery match the percentages in the contract data.
- The cumulative figures reconcile with the previous certificate.
Where AI fits
AI can reconcile an application with the BOQ and flag inconsistent quantities or arithmetic. It cannot decide what you are entitled to. The contract administration page explains what CAIS checks and what stays with your team.