Free Construction Retention Calculator
Calculate retention held and release dates for any UK construction contract. Enter your contract value, retention percentage, and practical completion date to see immediately how much retention is held, when the first tranche is due back under a 6+6 schedule, and when the final retention release is due. This calculator is free to use with no sign-up required and covers the standard 6+6, 12-month, and custom retention release schedules used in JCT, NEC, and DOM/1 subcontracts.
How to use this calculator
Enter the gross contract value (the total sum agreed in your subcontract), the retention percentage (typically 3% or 5% - check your contract particulars), and the practical completion date. The calculator will show you the total retention currently held, the 50% first release amount and its due date (6 months after practical completion for a standard 6+6 schedule), and the final retention balance with its release date (12 months after practical completion). You can switch between 6+6 and straight 12-month release schedules depending on your contract terms. The results update instantly so you can model different scenarios.
Retention in UK construction contracts
Retention is a percentage of each payment application withheld by the main contractor or employer as security against defective work. It is standard practice across UK construction subcontracts and is governed by the Housing Grants, Construction and Regeneration Act 1996 (the Construction Act), which requires that retention be released in accordance with the contract terms once the relevant conditions are met.
The most common retention rate is 5% of the gross value of each application, though many main contractors have moved to 3% retention in recent years following industry consultation. The retention fund accumulates over the course of the project and can represent a significant sum - on a £500,000 contract at 5%, the total retention held at peak can be £25,000. For subcontractors managing multiple contracts simultaneously, the aggregate retention held across all projects is often their largest single debtor.
Under the standard 6+6 retention release schedule, half of the total retention is released at practical completion. This is the formal event - usually certified by the contract administrator - at which the works are substantially complete and the employer takes possession. The remaining half is held for a further period (commonly 6 months) while the employer monitors the works for defects during the defects liability period (DLP). At the end of the DLP, once all defects identified in the schedule of defects have been remedied, the final retention is released.
Under a straight 12-month schedule, no retention is released at practical completion. The full amount is held until the end of the defects liability period. This structure is more common on smaller subcontracts or in contracts where the employer requires a higher level of security.
If the paying party fails to release retention on the due date, the Construction Act entitles you to refer the dispute to adjudication. In addition, the Late Payment of Commercial Debts (Interest) Act 1998 allows you to claim statutory interest at 8% above the Bank of England base rate on any overdue retention from the day after the release date. Use our Statutory Interest Calculator to quantify the interest owed on late retention payments.
BuildQS tracks retention held across all your projects automatically. Every payment application deducts the correct retention amount, cumulative retention is shown on your dashboard, and the platform sends automatic reminders when retention release dates are approaching. See our Retention Management feature for details.
Frequently Asked Questions
- What is retention in construction contracts?
- Retention is a percentage of each payment application that the paying party withholds as security against defective work. It is typically 3% to 5% of the gross value of each application and is released in stages after practical completion once defects have been remedied.
- What is the 6+6 retention release schedule?
- Under a 6+6 schedule, half of the total retention is released at practical completion and the remaining half is released at the end of the defects liability period - usually 6 months later. The full retention cycle therefore runs for approximately 12 months from practical completion.
- What percentage of retention is typically held on UK construction contracts?
- Retention rates typically range from 3% to 5% of the gross value of each payment application. 5% has historically been the most common rate, though many main contractors now apply 3%. The exact rate will be specified in your subcontract particulars.
- When is retention released?
- Under a 6+6 schedule, the first 50% is released at practical completion and the second 50% at the end of the defects liability period (usually 6 months later). Under a 12-month schedule, 100% is released at the end of the defects liability period. Your contract will specify the exact conditions that must be met before release.
- Can I claim interest on late retention release?
- Yes. If a main contractor or employer fails to release retention on the due date, you are entitled to claim statutory interest under the Late Payment of Commercial Debts Act 1998 at 8% above the Bank of England base rate, plus fixed compensation of £40, £70, or £100. Use our Statutory Interest Calculator to calculate the amount owed.
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