You need to reapply for Council Tax Reduction if your circumstances change. Otherwise, if your application is approved, you generally do not need to reapply each year unless asked to do so by Sevenoaks District Council.
It's important to stay updated on your status and report any significant changes that might affect your entitlement, such as changes in income or household composition. If you need to apply or report a change, you can do so via the Council Tax Reduction application page.