How do I report a stock sale when I don't have a 1099-B?

You should try to get a copy of the 1099-B.  However, it is not required to enter the stock sale and associated capital gains.  Use the instructions in the link below and when asked if you received a 1099-B, answer NO.  

Form 1099-B (Proceeds from Broker and Barter Exchange Transactions) reports the sale of stocks, bonds, mutual funds, and other securities.   Here's where you enter or import your 1099-B (even if you did not get one) in TurboTax:

1. Open (continue) your return if it isn't already open.
2. In TurboTax, search for 1099-B and then select the Jump to link in the search results.
3. Answer Yes to Did you sell stocks, mutual funds, bonds, or other investments in 2019?
   • If you see Here's the info we have for these investment sales, select Add More Sales.
4. Answer NO to Did you get a 1099-B or brokerage statement for these sales?  Or answer YES if you want to try to import it.
5. Follow the instructions.

Related Information:

• How do I enter a large number of stock transactions in TurboTax Online?
• Where is Form 8949?
• How do I report my child's investment income in 2019?

why no 1099-B? did you sell to a related party at a loss? in such a case the loss wouldn't be allowed.