Retention calculator — the pot, the claim cut, and the release dates

Retention is a percentage of every certified claim, held back by the client as security for completion and defects. The pot — the most that can ever be held — is simply the contract value multiplied by the retention percentage. Each progress claim gives up the same percentage of its certified value: claim 120,000 at 10% and 12,000 is held, 108,000 is what the certificate actually pays.

Release is usually in two slices. The first comes at practical completion — often half the pot, but the share is whatever the contract says — and the balance after the defects liability period ends. This calculator applies your three percentages to your two money figures; it does not invent terms. The percentages in a real job live in the signed contract, and where a cap on total retention applies, the contract states that too — check yours before you rely on any figure here.

Two contract shapes change the picture this calculator draws. Some contracts let the contractor swap the held cash for a retention bond or bank guarantee — the client keeps its security, the contractor frees the cash, and the pot becomes a fee instead of a freeze. And where retention flows down a subcontract chain, each tier may hold from the tier below on its own dates, which are not automatically the dates on which the tier above releases. Neither shape is a default: both live or die by the signed wording.

Running these jobs? Masonry & Plaster

The pot: 10% of 1,000,000 is 100,000 — the ceiling on what the client can hold across the whole job, reached claim by claim.

The claim cut: a certified claim of 120,000 loses 10%, so 12,000 joins the pot and the certificate pays 108,000. The releases: half the pot, 50,000, returns at practical completion, and the remaining 50,000 after the defects period — which is why the guide to retention money insists the release dates belong in a diary, not in memory.

A second shape, at the gentler rate common on larger contracts: a 2,400,000 contract at 5% gives a pot of 120,000 — half the rate of the first example, on more than double the value, and still the larger pot. A certified claim of 300,000 gives up 15,000 and pays 285,000; at a 50% completion release, 60,000 returns at practical completion and 60,000 after the defects period. Run the two examples side by side and the lesson stands out: the percentage is the headline, but the pot is the number your cash flow actually feels.