Assess as having no VAT to pay, nothing to reprove (4-4)

I believe the answer is:

zero-rate

'assess as having no vat to pay' is the definition.
(assess at zero for VAT purposes)

'nothing to reprove' is the wordplay.
'nothing' becomes 'zero' (synonyms).
'to reprove' becomes 'rate' (rate could historically mean to reprove or scold).
'zero'+'rate'='ZERO-RATE'

I've seen this clue in The Guardian.

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