How do I handle a wash sale if it involves two unrelated brokerage accounts? The first will issue a 1099 showing a loss; the other has no visibility to the sale.

you'll have to do it manually. neither the brokerages nor Turbotax can do this.

Enter your sales manually as Tax Champ Mike9241. In answering your question, I’m assuming your first sale with Form 1099B will show a loss without a wash sale.

 

When you enter your transaction, check the box The cost basis is incorrect or missing on my 1099-B.

 

On the screen, “We noticed there's an issue with your cost basis...Let us know if you'd like to make any changes” choose I know my cost basis and need to make an adjustment

 

Enter your cost minus your wash sale.

 

In your second transaction, if you do not have a 1099-B, enter the correct cost basis with the wash sale amount. If the second sale is reported on Form 1099-B, repeat the process with your first transaction, but add back the wash sale amount.