By Helen Reid

(Reuters) -Shein's British business made 1.55 billion pounds ($2 billion) in revenue in 2023, a filing by the online fast-fashion group showed on Tuesday, as it prepares for a hotly debated listing in London.

The annual revenue from the UK, Shein's third-biggest market, was 38% more than it had previously reported for a 16-month period to the end of 2022.

The group's rapid growth, fuelled by its low-cost business model of sending parcels to customers worldwide straight from factories in China, has disrupted the budget fashion industry and put pressure on incumbents such as Sweden's H&M and London-listed Asos and Boohoo.

Shein, valued at $66 billion in a fundraising last year, is set to hold informal investor meetings in the coming weeks for a planned London initial public offering, sources said last week, as the group awaits UK regulatory approval.

A multibillion-dollar IPO would be a boost for London, which has struggled to attract big company listings in the wake of Brexit. But lawmakers have also called for scrutiny of Shein's supply chain. The company has repeatedly said it is committed to respecting human rights.

Shein Distribution UK Ltd previously reported sales of 1.122 billion pounds over the 16 months from Sept. 6, 2021 to the end of 2022. It did not give a figure for the calendar year 2022.

The UK business booked a pretax profit of 24.4 million pounds in 2023, doubling from 12.2 million pounds over the previous 16 months.

Shein, which sells $5 tops and $10 dresses, does not publicly report its global results, but Coresight Research estimates it made $32.2 billion in sales worldwide in 2023, and that it could hit $50 billion in sales this year. By comparison, fast-fashion giant Inditex, which owns Zara, made 35.9 billion euros ($39.39 billion) in sales in its 2023 financial year.

Britain was Shein's third-largest market in 2023 after the United States and Germany, according to GlobalData estimates.

However, Shein's footprint in the country is small: the British unit hired an additional 19 people in 2023 for a total of 33 employees by the end of the year. The company's 2023 wage bill was 2.5 million pounds, and it paid 5.7 million pounds in tax.

In the filing, Shein said 2023 milestones included pop-up shops all over Britain, and opening an office in Manchester, northwest England.

Shein's business in Britain, the European Union and the United States benefits from customs duty exemptions on low-value parcels that allow it to send goods from China to shoppers' doorsteps largely tariff-free.

Some competitors say this gives the company an unfair advantage, and politicians have called for the exemption to be scrapped. Shein has said it wants to work with policymakers to review the customs frameworks.

As it tries to win over decision-makers in the UK and Europe, Shein in July pledged to invest in the region.

Almost all of Shein Distribution UK's revenue – or 1.39 billion pounds of it last year - are paid to its Singapore-based parent Roadget Business Pte Ltd. for purchases of the goods sold in the UK, the accounts show.

Shein Distribution UK Limited is a fully-owned subsidiary of Roadget Business Pte Ltd, and the ultimate controlling party is Elite Depot Limited, a company registered in the Cayman Islands, the filing shows.

($1 = 0.7638 pounds)

($1 = 0.9113 euros)

(Reporting by Helen Reid in London and Prerna Bedi in Bengaluru, additional reporting by Tom Bergin; Editing by Louise Heavens, Mark Potter and Susan Fenton)