There is a short window, roughly the two weeks around moving in, when every fact about a house is either in front of you or one phone call away. The previous owner is still reachable. The surveyor's report is still open on your laptop. The boiler manual is still in a drawer rather than lost.
After that window, each of those facts costs an afternoon to recover, and some are gone permanently. This is the highest return hour of admin in the whole process.
Day one, before anything else
These are time sensitive in a way the rest are not.
5 things to do
Ticks are for this visit only. Nothing here is saved anywhere.
Week one, while it is still accessible
5 things to do
Ticks are for this visit only. Nothing here is saved anywhere.
Read the survey once more, as a to-do list
The survey was read as a buying decision. Read it again now as a maintenance plan, because it is the only document that has systematically inspected the house and it usually names things that are fine now and will not be in three years.
Pull out anything with a timescale attached and give it a date. That is a maintenance schedule somebody else already did the hard part of.
The insurance detail people miss
If the property will be empty for a stretch between completion and moving in, check what your policy says about unoccupancy. Many lapse or reduce cover after thirty days empty, and the period around a move is exactly when that bites.
What this saves you later
A year on, the boiler needs servicing and you know when it was last done and by whom. Something fails under warranty and you have the serial number. An engineer asks how old the system is and you have an answer.
Which fields matter for each kind of thing, and where model plates hide, is covered in what to record about an appliance.