Asos revenues broke through £1 billion in the last four months of the decade as the online fashion retailer was lifted by a record Black Friday.
Retail sales hit £1.07 billion in the period ending on New Year's Eve.
Meanwhile, total group revenue, which also includes revenues from third parties, rose to £1.11 billion.
Both measures were 20% up on the year before.
The business said it had managed to "rebuild customer momentum", especially due to its best Black Friday on record. It did not reveal what proportion of its clothes were sold at a discount, or what sales were on the day.
Chief executive Nick Beighton said: "Asos has delivered an encouraging start to the year. Strong customer acquisition activity, supported by robust operational performance, has driven good momentum in all our markets."
Asos kept its outlook for the full year unchanged, and said it would focus on trying to retain the new customers who have started using its website.
The UK, while still the most important single market for the company, lost some of its revenue share.
UK retail sales hit almost £409 million, 18% up on the year before, but international retail sales jumped by 22%, including a 23% increase in the US.
It means that the UK's share of retail sales is 38%, down from nearly 39% a year earlier.
"As we said in October, the focus for this year is to further enhance our capabilities and leverage the investments we have made," Mr Beighton said.
The company shipped 27.7 million orders in the four months, a 20% rise on the same period in 2018. Meanwhile, 23% more visits to its website were clocked up.
EU retail sales rose 21% to £332.5 million.
Mr Beighton added: "We remain confident in our ability to capture the substantial opportunity ahead of us."
