Interim Payment Certificate Calculator

Work out interim payment certificate instantly with clear inputs, formula shown and shareable results.

About Interim Payment Certificate Calculator

An interim certificate values the work cumulatively, adds materials properly stored on site, deducts retention, then subtracts everything previously certified. Working cumulatively rather than period by period is what allows earlier valuations to be corrected without a separate adjustment.

Formula

Certificate

Net due = (work executed + materials on site) x (1 - retention rate) - previously certified

Worked example

With the default values below, Interim Payment Certificate Calculator returns Net payment due this certificate of $1,540,000.00. Change any input above and every figure here is recalculated in your browser.

Inputs used

Value of work executedminimum 0: 3,000,000
Materials on siteminimum 0: 200,000
Retention rateaccepts 0–20 %: 5 %
Previously certifiedminimum 0: 1,500,000

Results

Net payment due this certificate: $1,540,000.00
Gross valuation: $3,200,000.00
Retention deducted: $160,000.00
Cumulative certified after retention: $3,040,000.00

Step by step

1Values used
2Certificate
3Net payment due this certificate= 1,540,000.00
4Gross valuation= 3,200,000.00
5Retention deducted= 160,000.00
6Cumulative certified after retention= 3,040,000.00

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is the Interim Payment Certificate figure worked out?

Net due = (work executed + materials on site) x (1 - retention rate) - previously certified. An interim certificate values the work cumulatively, adds materials properly stored on site, deducts retention, then subtracts everything previously certified.

Why value materials on site separately?

The contractor has paid for them but has not yet earned the installed value. Including them at cost improves cash flow without paying for work not done, provided title and insurance are in order.

What values do I need to enter?

This calculator takes 4 inputs: Value of work executed, Materials on site, Retention rate, Previously certified. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.