Self employed spouse visa

[Andi4]

Hi there,
on the appendix fm se 7(a) Evidence of the amount of tax payable, paid and unpaid for the last full financial year.

I've been trying to work out what documents are suitable for this. I thought sa302 would do it but they ask for that aswell so it can't be it.

If anyone knows what's required for that please let me know.

Many thanks