Interest on every late invoice, billed in Xero in one go.
Free late-payment calculators work out one invoice at a time and leave the billing to you. Lateby takes your whole Xero invoice export and gives you three things they don’t: draft interest invoices ready to import into Xero (one per customer, one line per late invoice), a PDF notice per customer showing how each figure was worked out, and the whole batch for all your customers in one run. The UK statutory rate is picked per invoice from the Bank of England table. Nothing is uploaded: everything is made in your browser.
Your business details (printed on the PDF notices)
Saved in this browser only.
1. Your invoice export
In Xero: Sales (or Business) › Invoices › the All or Awaiting payment tab › select the invoices › Export. That CSV has each invoice’s due date and amount due. Xero’s Aged Receivables Detail report saved to Excel (.xlsx) works too. Paid, draft, voided and awaiting-approval invoices and credit notes are left out.
What the export cannot show: Xero’s export has no payment dates, so interest on invoices that were paid late but are now paid is not worked out. A part-paid invoice is charged on the amount still due today for the whole period, even if more was owed for part of it.
No export to hand?
2. Your interest rule
Bank Rate table used for the UK statutory rate (editable)
Each invoice gets 8% plus Bank Rate on the 30 June (interest starting 1 July–31 December) or 31 December (interest starting 1 January–30 June) immediately before the day interest starts to run, which is the day after the due date (Late Payment of Commercial Debts (Rate of Interest) (No. 3) Order 2002, article 4). A grace period does not change the rate. Figures from the Bank of England’s Bank Rate history, checked 26 October 2026. Add a line when a new half-year starts (e.g. 31/12/2026 3.75).
Lateby is a calculator, not legal advice. Charge interest only where your terms or the law allow it, and on business customers: interest on consumer debts is regulated differently.
3. The Xero import file
Free: the interest is worked out for every customer, and the import file and PDF notices cover the first 3 customers charged in each batch. The Practice plan covers every customer.
Practice plan active: import file and notices for every customer.
To import: in Xero, Sales › Invoices › Import, choose the file, and pick tax exclusive amounts. The interest invoices arrive as drafts for you to check, approve and send. Untick a customer to leave them out.
- Every late invoice, worked out the same way. Amount overdue × rate × days late ÷ 365, rounded per invoice, with a grace period, a minimum charge and an “already billed up to” date so a monthly run never charges the same days twice.
- Straight back into Xero. One draft interest invoice per customer, one line per late invoice, with the calculation written in the line description, in the column layout of Xero’s own invoice import template.
- A notice your customer can check. One PDF per customer listing each late invoice, the days and the interest, with your payment details and the clause in your terms.
- Private by design. Your export never leaves your computer. No Xero connection to approve, nothing stored on a server, no emails sent for you.
Interest on late invoices is one of the most-voted requests on Xero’s product ideas forum: “Sales Invoices – Add interest to late invoices”. Lateby is independent and is not affiliated with, endorsed by or connected to Xero. Xero is a trademark of Xero Limited.
Also from us: Carrytick turns client bank statement PDFs into Xero import files, and Ageline makes customer statements with 30/60/90-day ageing.