If bacs credits and bank transfers are included in budgets/Summary, which would be very useful from a budgeting standpoint (eg: if someone transfers you their part of a transaction via bank transfer or a refund is received via bacs credit), then an Income category would be required to prevent the category which you assign your salary (or the transfer of spending from another bank account) being completely overpowered by the incoming salary. This Income category would also need to not count towards any overall budget set in Summary and the ability to set a budget for the Income category also wouldn’t be needed.
For example: if you assign your salary to General, then the General category will always be positive, preventing you from budgeting for spend assigned to that category. Any overall budget would also be affected by this income.
An alternative option would be to not give any incoming transactions (not from Bill Splits) a category (ie: their category would be unassigned), but that basically sounds like an “unassigned” category would have to be created. In that case, it would be a better UX to just call that category “Income” and give it a logo.