Late payment interest

How to Use This Calculator

Enter the overdue principal, payment due date and calculation date. Select the interest basis that applies and enter the relevant reference rate and additional percentage points. Keep the rate source and the contract provision with the calculation.

Worked Example

For a purely numerical illustration, £10,000 at an assumed 12% annual simple-interest rate for 30 days gives £98.63 of interest on a 365-day basis. That assumption is not a statement of the current Bank of England rate.

Before You Use the Result

The tool does not establish that a debt or interest entitlement is accepted. Confirm the applicable interest basis and any eligibility for fixed compensation before using the output in a payment request.

For a project that needs a wider review, explore QSEC claims and dispute support alongside The Subbie QS support.

Return to the full QS tools library for related calculators. You can also read about our payment application support or use the free QS templates to organise the underlying records.

Use The Working Sheet For This Task

Organise current value, previous work, this period, retention and the supporting records.

Download the Payment Application Sheet (Excel)

Record the notice dates, owner, service route and proof required by your signed subcontract.

Download the Notice & Deadline Register (Excel)

Each Excel link takes you to the matching sheet preview. Enter your work email to download, replace the example entries and start using the file on your job. Marketing is optional.