GOV.UK
When a Stamp May Be Applied: Subject to certain exceptions, relevant products must bear a duty stamp at the time that they pass a UK duty point
Traders are free to apply stamps at any point between bottling and removal to home use onpayment of duty. In practice, this has different implications for different types oftrader. But for label stamps, in all cases, the label stamp is affixed to the retailcontainer at the time the label is applied to the bottle.