My experience in this area is with Fidelity and Schwab. If you have different 1099's with different SSN's that belong on one return, when you import, both Schwab and Fidelity will list all the accounts. You then check off what you want downloaded. In the past, I'd check which 1099's I wanted to download - and check that. Then it would download. When I go back and import say, something I forgot or for a different family member, I'd download that account. I've never had Turbo Tax delete what was previously downloaded automatically. Ive' been doing this for at least 5 years and have never seen this problem before.
