Tracking Expenditure in categories and sub categories

I’m trying to build a simple database that will track monthly expenditure that will come from a bank statement. I want to be able to categorise the expenditure with categories and sub categories possibly three sub categories deep so I can then see totals by month and by main or sub categories.

What would be the best way to achieve this?

Group by category, groupupwithin subcategories and voila!

I’m assuming that I’d need a field categories and a field subcategories?

Exactly correct.