Most contractors don't skip documenting changes because they don't care. They skip it because starting from a blank page every time feels like too much friction in the middle of a job.
A template fixes that. Here's one you can copy as is.
The template
Customer name:
Project:
Date:
What's changing (plain language, one or two sentences):
Materials cost:
Labor (hours x rate):
Markup:
Total price to customer:
Customer approval (signature, text confirmation, or email reply):
A filled-in example
Customer name: Maria T.
Project: Kitchen remodel
Date: March 12
What's changing: Upgrading the countertop from laminate to quartz
Materials cost: $840
Labor: 4 hours x $65/hr = $260
Markup: 20% = $220
Total price to customer: $1,320
Customer approval: Confirmed by text, March 12
Why this format works
It's short enough to fill out in two minutes on site, and it captures everything that actually matters if a question comes up later: what changed, what it cost, and that the customer agreed to it before the work happened.