Free tool
IPC and retention calculatorfor Saudi construction contracts
Put your contract terms and this period's measure in, and the certificate computes itself: retention held against the cap, the advance recovered pro-rata, the net certified to date, what is payable this period and the VAT on it. Everything runs in your browser — nothing is sent anywhere, and no figure here comes from us.
Interim payment certificate calculator
Every figure here comes from your own contract and your own measure. Nothing is assumed — change a term and the certificate re-computes. It runs in your browser; nothing is sent anywhere.
Recovered pro-rata against work done.
Most Saudi contracts cap retention at 5–10% of the contract sum. Use your own figure.
The net cumulative of every certificate before this one.
How it works
What this IPC and retention calculator actually does
Four bits of arithmetic that a spreadsheet usually gets subtly wrong, and one that it gets wrong loudly.
How the IPC and retention calculator handles retention
Retention runs on measured work rather than on materials on site, and it stops at the contract cap. A spreadsheet that keeps deducting past the cap quietly overstates what the client is holding — and understates what you should be chasing.
- Percentage on measured work
- Capped at the contract limit
- Cap breach flagged when it happens
Advance recovered pro-rata
The advance is recovered in the same proportion as the work completed, so it is fully recovered exactly as the contract is. Recovering it faster starves the project of cash; slower leaves you exposed at the end.
- Recovery follows completion
- Never over-recovers
- Shown as its own line
Gross, net and previously certified
The number that matters this month is the net cumulative minus everything certified before it. Getting the cumulative basis wrong is the single most common reason a certificate comes back.
- Cumulative, not periodic
- Previous certificates deducted
- Net this certificate shown alone
VAT on the right figure
VAT applies to the net certified this period, not to the gross measure and not before retention. Getting it wrong is the version of this error that a ZATCA rejection makes loud rather than quiet.
- VAT on net, not gross
- Rate as an input
- Ready to reconcile to the invoice
Related:how IPC and progress billing works in the systemsubcontractors and retentionVAT on retention in Saudi constructionthe GOSI and payroll cost calculator
FAQ
Frequently asked questions
Is this IPC and retention calculator free to use?
Yes, and there is no sign-up, no email wall and no limit. It runs entirely in your browser: the figures you type never leave the page and are not stored anywhere. Use it on a live certificate, use it to check a client's own figure, or use it to sanity-check a spreadsheet before you submit.
Does retention apply to materials on site?
Under most standard forms, no — retention is deducted against measured work executed, and materials on site are certified separately without retention against them. This calculator follows that convention. Contracts do vary, so read the particular conditions of yours; if it says otherwise, add the materials into the work figure instead.
How is the advance payment recovered?
Pro-rata against completion: if you have completed 40% of the contract, 40% of the advance has been recovered. That way it is fully recovered exactly as the works complete. Some contracts specify a different recovery profile, such as starting after a threshold — in that case use the recovered-to-date figure your contract produces rather than this default.
What is a retention cap?
A ceiling on the total retention the client may hold, usually expressed as a percentage of the contract sum — commonly 5% or 10% in Saudi contracts. Once the running deduction reaches it, no further retention is withheld. The calculator flags the certificate where that happens, because it is the point a spreadsheet usually keeps deducting and nobody notices for months.
Is VAT calculated on the gross or the net figure?
On the net certified for the period — after retention and after advance recovery — not on the gross measure. Charging it on the gross overstates the invoice and is the kind of error a ZATCA clearance surfaces immediately. The rate is an input here so you can model a different one if your situation requires it.
Can I use this instead of a proper system?
For one certificate, yes, and that is what it is for. What it cannot do is carry the audit trail: which BOQ lines were measured, who approved the variation, what the subcontractor's back-to-back certificate says, and whether the resulting invoice cleared. When you are running that across several live projects, a calculator stops being the right tool — but you should not need a system to check one number.