Estimates the cash retention a JCT employer may hold from a certified value, and the two-stage release: one half at Practical Completion, the balance after making good defects.
Indicative cashflow only. Verify against the Contract Particulars (JCT SBC clause 4.18).
For cashflow guidance only. Always verify against your contract and a qualified surveyor.
About this retention calculator
This free retention and cashflow calculator works out the cash retention a JCT employer may hold back from a contractor’s certified value, and the two-stage release of it: one half at Practical Completion and the balance after making good defects. Enter the gross certified value of work properly executed, the Retention Percentage from the Contract Particulars, the contractual Retention Limit, the fraction released at Practical Completion and the rectification period, and the calculator returns the sum held, each release tranche and the percentage still held through the defects period. It is aimed at UK contractors, quantity surveyors and commercial managers forecasting cashflow on a JCT Standard Building Contract. All figures are computed in your browser; nothing is uploaded.
How retention is calculated
The method follows the JCT Standard Building Contract (SBC 2016/2024), clause 4.18, the Rules on Treatment of Retention. The retention is the Retention Percentage × the total value of work properly executed, then capped at the contractual Retention Limit: held = min(value × %, limit). The JCT default Retention Percentage is 3% (commonly amended to 5%). One half of the held retention is released in the certificate at or immediately following Practical Completion; the remainder is released in the next certificate after the Certificate or Notice of Completion of Making Good Defects, which follows the rectification period. This calculator models that final tranche at the end of the rectification period (JCT SBC default six months, often amended to 12 or 24). The percentage still held through defects is the Retention Percentage × (1 − the fraction released at Practical Completion). Build UK’s Minimum Standards on Retention confirm half-release at PC and the balance after defects as standard JCT practice.
Frequently asked questions
What retention percentage should I use?
The Retention Percentage is set in the Contract Particulars. The JCT Standard Building Contract default is 3%, but it is frequently amended to 5%. Use whichever figure your contract states. The percentage applies to the total value of work properly executed.
When is retention released?
Under JCT SBC clause 4.18 half of the held retention is released at Practical Completion, and the remaining half is released after the Certificate or Notice of Completion of Making Good Defects, once the rectification period has run and any defects have been remedied.
What does the Retention Limit do?
The Retention Limit is the maximum total sum the employer may hold. When the percentage-derived retention exceeds the limit, the held sum is capped at the limit and both release tranches are calculated from that capped figure. Set the limit high to make the cap non-binding.