(Reuters) -China-founded fast-fashion retailer Shein plans to file a draft prospectus confidentially for its Hong Kong listing, marking a rare departure from the usual practice of companies making public filings of IPO documents, three sources with knowledge of the matter said.

Shein aims to submit the filing confidentially as soon as this week, one of the sources said. A second source said the filing was expected to be made by Monday.

Shein's confidential filing, if approved, would represent a waiver of one of the main listing rules by the Hong Kong exchange for one of the world's most closely-watched IPO candidates, and possibly the largest in the city this year, two of the sources said.

The filing will come as the company, which sells low-priced apparel such as $5 dresses and $10 jeans in around 150 countries, makes its third attempt to go public, more than 18 months after it first filed for a U.S. IPO in late 2023.

Confidential filings enable companies to keep vital operational and financial information under wraps for longer and allow them to go through the regulatory review process without public disclosure.

Hong Kong's listing rules permit confidential filings for secondary listings by companies already listed on recognised overseas exchanges, such as the New York Stock Exchange or Nasdaq.

The exchange could also waive or modify the publication requirements in a spinoff from an overseas listed parent upon application by a new applicant, the listing rules show.

While this practice is common for IPO applicants in the U.S., it remains relatively rare in Hong Kong, where high-profile IPOs have included Chinese tech giants Xiaomi and Meituan, which both filed publicly for their floats.

The sources spoke to Reuters on the condition of anonymity as they were not authorised to speak to the media.

Shein, founded by China-born entrepreneur Sky Xu, did not reply to a request for comment. The Hong Kong stock exchange declined to comment on individual companies.

Documents, including financials, related to Shein's IPO will remain undisclosed until the company passes a hearing with the Hong Kong stock exchange, which is the final step in the city's regulatory approval process.

Prior to that final step, Shein must secure an approval from the China Securities Regulatory Commission (CSRC) to go ahead with the Hong Kong IPO. It is not known if Shein has already secured a verbal nod from the Chinese securities regulator.

The CSRC did not respond to Reuters request for comment.

Reuters first reported last month, citing sources, that Shein was working towards a listing in Hong Kong after its proposed London IPO failed to secure the green light from Chinese regulators.