How do I change how my expenses are categorised? At the moment they are all going to 'phone fax stationery' on the income tax page

Your expenses are going to "Phone, fax, stationery and other office costs" because of how your Chart of Accounts is set up. If you chose Office/General Administrative Expenses as the Detail type, that’s where the expenses will be recorded.
 

To change this, select Other Miscellaneous Service Cost as the Detail type instead. This will move those expenses to "Other business expenses" on your Income Tax page.
 

Also, check your Bank Rules on the Banking page. You might have a rule that automatically categorizes your supplier expenses as "Phone, fax, stationery." If so, update or remove that rule to fix the issue.
 

I also recommend consulting your accountant for personalized guidance.
 

Let us know if you have further questions or concerns.