Almost everybody keeps the invoice and forgets everything else. The invoice tells you what you paid. It rarely tells you what was actually wrong, what was replaced, or what the engineer said would need doing next.
That second set is what makes the next repair faster, and it exists only in your memory for about two weeks.
Write these down the same day
6 things to do
Ticks are for this visit only. Nothing here is saved anywhere.
The diagnosis is worth more than the invoice
When the same appliance misbehaves in two years, the single most useful sentence is what an engineer concluded last time. It shortens the next visit, and it sometimes prevents one entirely because you recognise the symptom.
It also protects you. An engineer telling you a part was replaced eighteen months ago is a very different conversation from one where nobody can remember.
Record what they said would come next
Engineers routinely mention that something else is nearing the end of its life, and that remark is almost never written down. Six months later the thing fails and nobody remembers being warned.
That one line is the most valuable thing in the whole visit, because it is the only genuinely predictive information you will get about your own house.
Keep a note of who to call again
Finding a good tradesperson is harder than any of the admin around it, and most people rediscover this every few years because the number was in a text message that got lost.
Recording who came, alongside the thing they worked on, means the next problem starts with a phone number rather than a search.
This is also what makes maintenance schedules real
A service interval only means something if you know when the last service happened. Without that, every schedule starts from an arbitrary date and drifts.
The intervals themselves are in how often things actually need servicing.