Cross matching income and expenditure

i have a list of categories in my budget such that i would desire ALL entries under invoices (i.e revenue/income) and bills (i.e purchases or expenditure) would be effectively captured.

My question is, when creating a bill under the 'Account VAT Rate' column, how do i CHANGE/TRANSFER the categories under 'Administrative Expenses' to 'Cost of sale'?

See portion of screenshot