Free tool
Construction retention calculator
Retention is a percentage of the value of work done that the payer holds back as security that the job will be finished and defects put right. It is commonly 3% to 5%, often capped at around 3% of the contract sum, and released in two halves: one at practical completion and the balance at the end of the rectification period. This works out what is being held on a valuation, whether the cap or the rate decided it, and the dates both halves fall due.
Last reviewed by Estimark. This page states periods and rates set by statute or by standard contract terms. Those move, and this date is when somebody last read the page against its source rather than the day the site was built.
Retention
What is being held, and when it comes back
Nothing is sent anywhere and nothing is stored. No statute sets a retention rate, so every figure here is a contract term you can change.
Cumulative, not this month alone. Retention is taken on the running total.
Comes off after retention, not before.
Held back on this application
£5,000.00
5% of £100,000.00 valued to date.
- Value of work to date
- £100,000.00
- Retention at 5%
- − £5,000.00
- Cap, not yet reached
- £7,500.00
- Already certified
- − £0.00
- Certified this application
- £95,000.00
Getting it back
At practical completion£2,500.00
20 September 2026
End of the rectification period£2,500.00
20 September 2027
The second release is conditional on defects being made good, and an open snag nobody closed out is the standard reason it never becomes payable. Photograph each item as it is finished and send the evidence at the time.
Estimark holds retention against the job, deducts it on every application in this order, and puts the release dates in the diary at practical completion so the second half is chased rather than written off. How retention works in Estimark.
How much retention is held?
Whatever the contract says. No statute sets a rate, and in UK construction it is commonly 3% to 5% of the value of work done, with the total often capped at around 3% of the contract sum.
- It is taken on the cumulative value of work done, not on this month’s increment alone.
- It comes off before the previously certified total does. Reversing those two produces a plausible figure that is wrong on every application after the first.
- Once a cap is reached, retention stops accruing however much more work is valued.
The percentages here are what the standard forms commonly say. They are defaults in a calculator, not terms in your contract.
When is retention released?
In two stages under most standard forms: half at practical completion, and the balance at the end of the rectification or defects liability period.
- The money is yours throughout. Retention is a deduction from a payment, not a reduction in the contract sum.
- A rectification period is counted in whole months from practical completion, so twelve months is the same date next year rather than 365 days on.
| Stage | What is released | What has to happen first |
|---|---|---|
| Practical completion | Commonly half of what is held | The certificate is issued |
| End of the rectification period | The balance | Defects made good, commonly 6 or 12 months later |
Why does the second half so often go unpaid?
Because it is conditional, and nobody chased the condition. An open snag list is the standard reason a payer never releases the balance.
- Photograph each defect as it is made good and send the evidence at the time rather than as a bundle at the end.
- Diarise the release date at practical completion. A release nobody asks for is not usually refused, it is forgotten.
- Where the payer becomes insolvent, retention held in their general account ranks as an unsecured debt. That risk is the argument for a retention bond or a project bank account.
A calculator can tell you the date. It cannot tell you the snags are closed, and that is the half that decides whether you get paid.
Common questions
- How is retention calculated?
- As a percentage of the cumulative value of work done, deducted before the previously certified total comes off. On a £100,000 valuation at 5%, £5,000 is held and £95,000 is certified, less whatever has already been paid.
- What is the normal retention percentage in UK construction?
- Commonly 3% to 5% of the value of work done, often capped at around 3% of the contract sum and usually halved at practical completion. There is no statutory rate; it is whatever the contract says.
- When is retention released?
- In two stages under most standard forms: half at practical completion, and the balance at the end of the rectification or defects liability period, commonly six or twelve months later and conditional on defects being made good.
- Is retention still my money?
- Yes. Retention is a deduction from a payment rather than a reduction in the contract sum, so the sum remains owed to you. The risk is not that it stops being yours, it is that the payer becomes insolvent while holding it, or that a release nobody chases is never made.
- Does this calculator store anything?
- No. The arithmetic runs in your browser. Nothing is sent to a server, nothing is stored, and there is no email address to give.
Payment applications & retention
Construction Act dates, pay less deadlines and retention tracked to release.
ReadRetention in construction contracts
Why it is held, how it is released, and the reasons the second half goes unpaid.
ReadWhat is practical completion?
The event that starts the rectification period and releases the first half.
ReadFor builders & contractors
Job costing, CIS, payment applications, site safety, plant and fleet.
Read