This was homegrown stuff we did; the credit bit is from their 2013 annual[0], under "Revenues -> Automotive Sales". This discusses the start of their credit sales. The 2013 Q1 [1] shows a ~11m net income; later, they discuss credit sales [2]. Then, the market went nuts over >0 net income: this 2013 article [3] seems like a reasonable summary.

You can find the reports from ir.teslamotors.com/sec-filings or the SEC's Edgar database.

[0] https://ir.teslamotors.com/node/12956/html#tx452995_10

[1] https://ir.teslamotors.com/node/13166/html

[2] During the first quarter of 2013, we recognized $67.9 million in ZEV sales, which contributed to our gross margin. ZEV credit revenue should decline in future quarters relative to our automotive sales as we grow our sales outside the United States and earn fewer credits on the 60 kWh Model S battery variant for those sales that occur in the United States. Other regulatory credit sales recognized during the first quarter of 2013 were $17.1 million. While we will pursue opportunities to monetize ZEV credits we earn from the sales of our vehicles, we do not plan to rely on these sales to be a significant contributor to gross margin, and our business model is not predicated on such ZEV credits."

[3] https://www.reuters.com/article/autos-tesla-debt-idUSL2N0DY1...