Organisations, including sole traders, that use personal information must pay a data protection fee to the ICO unless they're exempt. The fee is paid every year.
When it renews
Your fee runs for a year from when you registered, so the renewal falls on the same date each year. Your ICO registration shows it.
If you don't pay
The ICO can take enforcement action and issue a fine for not paying the fee.
Get reminded before it's due
Regmindr tracks this and the rest of your FCA calendar, and emails your team before each deadline. Set it up from your year end in about two minutes.
Sources
This page is a summary, not legal or regulatory advice. The rules in the sources above take precedence.