The discount retailer, owned by American private equity firm TPG Capital, is understood to be in talks with investment firm Rcapital, whose current portfolio includes property consultants Cluttons and cosmetic surgery firm The Harley Medical Group.
The filing gives Poundworld protection as it seeks to secure a deal, which would lead to store closures and an administration would be handled by Deloitte.
It allows its staff and suppliers to continue to be paid.
TPG had already been considering a restructure which would lead to 100 of 355 outlets being shut, putting 1,500 jobs at risk.
Earlier this week, talks with potential buyer Alteri Investors, whose website says it specialises in “challenging retail situations”, broke down.
About 100 Poundworlds were already under threat of being shut, but were kept open while takeover talks took place.
Poundworld, which also trades under the name Bargain Buys, has two million customers a week.
Poundworld has been losing money for the past two years. Losses for the financial year 2016-17 were £17.1million, up from £5.4million the year before.