A lapsed badge, plate, or DBS check stops you working. Enter your renewal dates once — they're saved in this browser so they're here next time — and download a calendar reminder for each one so your phone nags you, not a council letter.
Everything you enter is saved only in this browser (localStorage) — nothing is sent to a server, there's no account, and no one else can see it. That also means it won't follow you to a different phone or browser automatically — download the calendar file for anything that really matters, since that lands in your actual phone calendar and survives a browser reset.