To what lengths can you go to obtain financial documents?
The temptation is to keep paperwork received in the post for your ex-partner/spouse, to be able to use this in the financial dispute. However, any document belongs to the person it was sent to. Opening someone else's post is a criminal offence and permanently taking their post is theft. Interfering with a document that belongs to another is a tort.
The law does recognise the fact that there is an obligation to produce the documentation in financial proceedings. Where someone is not complying with this obligation by withholding material documents, it can be in the interests of justice for a party to be able to produce copy documentation to prove this. The Court has to consider what is necessary for disposing fairly of the case.
You are not allowed to intercept post or break into (for example) a desk, a locked room or a vehicle to gain access to documents. You are allowed to copy any documentation left "lying around" as long as you do not keep the original. You are also potentially allowed to photograph documents through windows and produce copies that way. However, the law is less clear in this area.