Interest Calculator – calculate interest on an unpaid invoice

You can charge interest and compensation on any invoices which have been paid late or have not been paid within your agreed payment terms. 

The interest you can charge if another business is late paying for goods or a service is ‘statutory interest’ – this is 8% plus the Bank of England base rate for business-to-business transactions. You cannot claim statutory interest if there’s a different rate of interest in a contract. 

Please note: 

• You cannot charge late payment interest until your invoice becomes overdue. 
• You cannot charge interest on an unpaid interest or compensation invoice. You can only charge interest and compensation on the original invoice which has been unpaid or has been paid late.  
• Unless terms are agreed, both public and private sector payment terms are 30 days. 
• Please note you can only collect interest on a late payment up to a maximum of 6 years from the from date following end of contracted payment terms. 

Using the Interest Rate Calculator  

Our interest rate calculator calculates interest to the first two decimal points only. While this gives a fairly accurate figure it should be used as a guide to the amount of interest and compensation you can charge on overdue invoices. Further details on late commercial payments can be found here. 

For guidance on our calculator and how to use it, please visit our interest calculator guidance page. 

If you have an invoice which has not been paid, you can contact us at the Office of the Small Business Commissioner (OSBC), as we may be able to assist you with recovering late payments.  

Details how we can help can be found here: How to Raise an Enquiry Regarding Late Payments to OSBC – Small Business Commissioner