The MP3 site allows users to make online copies of CDs they already own.
It hit the headlines when major record labels sued it for allowing users to store copies of their own CDs online.
In the last three months Morissette has already sold $1.5m (£1.05m) worth of shares in the controversial company.
MP3.com recently reached a $53.4m (£37.1m) settlement with Universal, and $40m (£28m) deals with other firms.
Morissette filed her intention to sell the latest batch of common stocks with the US Securities and Exchange Commission (SEC).
The SEC document shows that the Canadian-born singer acquired all her MP3.com shares in April 1999.
MP3.com sponsored a tour by Morissette and Tori Amos in 1999, granting her management company shares in the company for 33 cents each.
Settlements
The company's deal with Universal allows it access to its back catalogue in return for the $53.4m.
However, MP3.com could face fresh legal challenges from other major record companies in future.
It previously made smaller settlements with Sony and Warner Music. US trade paper Hollywood Reporter reported these firms might begin legal action to increase their deals.
Morissette's biggest hit singles include Thank U, Ironic and You Learn but she is also well-known for the worldwide success of her album Jagged Little Pill.
The album won her several music industry awards, including Grammys for Album of the Year, Best Female Vocal Performance, Best Rock Song and Best Rock Album.
He follow-up album Supposed Former Infatuation Junkie was released in 1998 and has gone on to sell more than 7m copies.