British online fashion retailer Asos on Wednesday forecast a full-year profit at the top end of market forecasts after Christmas trading surpassed its expectations helped by strong demand during Covid-19 pandemic lockdowns.

Analysts have forecast a pretax profit of £115 million to £170 million ($157 to $233 million) versus £142.1 million in 2019 to 2020.

Asos, which sells fashion aimed at 20-somethings, said group retail sales rose 23 percent over the four months to December 31 year on year.

The group has traded through coronavirus lockdowns while store-based rivals have had to close shops for months.

It also benefited from fewer products being returned by shoppers during the crisis, as well as investment in product, pricing and marketing, it said.

Its active customer base increased by 1.1 million to 24.5 million, Asos said.

However, its gross margin fell 90 basis points, partly reflecting changes to its product mix and increased freight costs.

The group said it would incur Brexit tariff costs of about £15 million in 2020 to 2021 associated with country of origin rules.

Asos shares, up 57 percent over the last year, closed Tuesday at 5,196 pence, valuing the business at £5.1 billion.

By James Davey; editors: Estelle Shirbon and Jason Neely.