Check bond numbers locally
Import a winning-numbers ZIP that you downloaded from NS&I, then compare your bond numbers in this browser.
Open the local checkerIndependent • private by default
A clearer way to check bond numbers and understand your returns
Check Premium Bonds provides independent, browser-based tools for comparing bond numbers with an NS&I file you download, estimating odds and tracking returns. Your checker inputs stay on your device. We cannot access an NS&I account or confirm a prize, so always use the official NS&I Prize Checker for account-level results.
◆ Data privacy◆ Local-only tools◆ Independent guidance
Choose your task
Understand the odds
Build a scenario using source-reviewed parameters. If current facts are not verified, the calculator stays unavailable rather than guessing.
Open the calculatorTrack actual returns
Log prizes manually and calculate an annualised return. Saving on this device is always opt-in.
Open the return trackerHow local checking works
- You open the official NS&I downloads page.
- You download the monthly winning-numbers ZIP.
- You select it in the checker, where a Web Worker validates and indexes it locally.
- You enter bond numbers and receive matches only for your imported dataset.