A significant stake in Rivian Automotive, a start-up that develops electric cars, including Amazon’s commercial delivery vans, was revealed by the retail giant on Friday.

According to an SEC filing, Amazon has equity assets “including preferred shares of Rivian Automotive, Inc. reflecting an approximately 20% ownership stake” with a carrying value of $3.8 billion as of Sept. 30, compared to $2.7 billion as of Dec. 31.

Rivian stated in a separate securities filing earlier this month that Amazon has invested more than $1.3 billion in the company so far.

Rivian announced it aims to list on the Nasdaq under the ticker code “RIVN” after filing its IPO prospectus on Oct. 1.

The filing offered additional information about how tightly Rivian and Amazon are linked. Rivian is planning an initial public offering (IPO) in November.

Amazon has exclusive rights to Rivian’s electric delivery cars for at least four years, with the right of first refusal beyond that, according to Rivian. By 2030, Amazon has placed an order for 100,000 automobiles. Rivian expects to have 10,000 new electric delivery vans on the road by the end of next year.

Rivian is also owned by Ford Motors, which has a stake of more than 5%. Alexandra English, a former Ford executive, quit the Rivian board of directors in May, according to the company’s IPO prospectus released this month.

(Adapted from CNBC.com)