How to pay tax due on savings interest without completing a Self Assessment tax return

When I complete the 'Check if you need to send a Self Assessment tax return' on line it tells me I don't need to. However I've calculated I need to pay tax on savings interest; how do I do this without completing a Self Assessment?

Hi Andrew,
Your banks and building societies will inform us automatically of any savings interest accrued.
If any tax is due on these amounts, we will contact you to confirm how to pay online, or through your tax code.
Tax on savings interest
Thank you.