A gas safety certificate lasts twelve months. A boiler service is due once a year. An electrical inspection on a rental is every five. Each of those has a date on it, and almost nobody puts the date anywhere useful.
The landlord with four flats has a vague memory that the gas certs are due in autumn. The homeowner whose boiler you fitted in March 2024 has no idea it should have been looked at twice by now. You have the dates, somewhere, on the certificates you issued, in PDFs in Sent, and in a notebook from two vans ago.
So the system keeps the dates. Each time you issue a certificate or log a service, the next due date is recorded against that customer and that address. Six weeks before it falls due, the customer gets a short message: the gas safety certificate for 14 Elm Road expires on 12 March, here is a link to book. The link shows slots from your real diary. They pick one, it lands in your calendar, done.
If they do not book, a second nudge goes at three weeks. After that it stops. Nobody likes being chased for a service.
The useful part is where the work lands. Services and certificates are the jobs that can be done in January and February, when nobody is ringing about a new bathroom. A diary that fills itself in the quiet months is worth more than one more lead in June.
Landlords in particular notice. A reminder before the certificate lapses, rather than a fine after, is the kind of thing that keeps them on your books for years.
We build it on top of Google Calendar and whatever you issue certificates from today. How many of last year's customers have you heard from since?