You know the gathering evidence thing...

[dimots]

What can you do if absolutely everything is online & password protected? Bank statements, savings accounts, payslips, absolutely everything. How can you be sure that the other party has declared everything? My sister wants a divorce, but this is the situation with her. BIL is a high earner, but she has no idea how much money he has, the finance were always separate.

Have a look into forensic accountants.

Wouldn't that be very expensive though? He is on PAYE and so far she has no particular reason to think he his hiding anything - but how can she know? She hasn't got a lot of money herself and has been made redundant from her job.

In that case his P60 will have his earnings.

Keylogger, and I didn't say that.

Keyloggers wouldn't work. He only accesses this stuff on a works laptop which has a constantly changing encrypted pass code. I think his P60 is also only online. And that wouldn't show details of pensions or savings anyway. She knows roughly how much he earns, but not how much he has put away.