Tons cutting outside income contributing to government revenue (9)

'government revenue' is the definition.
The definition suggests a singular noun which matches the answer.

'tons cutting outside income' is the wordplay.
'tons' becomes 't'.
'cutting' becomes 'axing' (I've seen this in another clue).
'outside' is an insertion indicator (some letters go outside others).
'income' becomes 'pay' (income from a job).
'axing' placed around 'pay' is 'axpaying'.
't'+'axpaying'='TAXPAYING'

'contributing to' is the link.

Can you help me to learn more?