AIBU to ask you to help me find passports? Other uses apart from travel?

[Walkingalot]

Sorry, not really AIBU but posting for traffic.

I last went on holiday with my DS approx 3 yrs ago. Was going to set up a bank acct for DS online and needed his passport. Can't find it in the usual place.
Racking my brain to think of the last time I had my passport out. I have a feeling I had to provide my passport number to prove my identity for something. I've tried googling but just come up with stuff about fraudsters. Any idea's on other uses, apart from travel? It might help job my memory.

I needed them as ID for childrens Covid tests recently.

For a DBS check.

For my mortgage.

How old is your DS and could he have moved it?
Otherwise school or benefit applications, sports (eg for football you'd have to provide his passport for FA player registration)?

Proof of ID for bank, jobs, solicitors.
Countersigning someone elses passport application.

Could you check in thr suitcases or flight bags?

I lost mine once and found it months later (after I had cancelled it and got a new one!) in the top of my photocopier/printer.