Yahoo has sent out letters to a number of potential buyers for its core business, asking them to submit preliminary proposals by 11 April, just under two weeks from now.

According to the Wall Street Journal, potential bidders are being asked to list which parts of the company theyd like to bid for, and how much they are willing to pay, as well as how they plan to finance any such deal, and details on the internal approval process behind any potential deal.

Recent reports suggest that around 40 companies have signed nondisclosure agreements with Yahoo in the last few months, enabling them to review materials about its business and eye up some or all of its core business units for a potential bid. Among the frequently rumoured buyers are mobile operators AT&T and Verizon, as well as private equity firms like KKR and TPG.

A report on Re/code last week also claimed that Microsoft was interested in purchasing at least part of Yahoos business, and was willing to financially support private equity firms that might be interested in buying the company.

Yahoo hasnt commented on the potential sale of any of its units, but the company is rumoured to be asking for $10bn for the complete core business. The internet giant has had a troubled few years, and efforts by CEO Marissa Mayer to restructure the firm into a more modern, mobile-focused business have been largely unsuccessful.

The last few months have seen Yahoo lay off around 15 per cent of its staff and shutter a number of services in an effort to streamline itself, but has still seen ad revenues drop by roughly 15 per cent at a time when rival firms are growing. Its market share of digital ad revenues is now only around 1.5 per cent of total industry spending.