Is it necessary to mail Form 1099-B if I e-file?

It may not be necessary to mail it in, but the IRS does want a copy of your wash sale 1099-B.

The IRS requires a copy of your Form 1099-B when you’re reporting transactions by sales section totals, rather than reporting each transaction separately, and you either:

• Made adjustments to your investment income, or
• Your cost basis isn’t reported to the IRS

Since an adjustment is typically required with a wash sale, the IRS needs a copy of the 1099-B.

However, if you're using TurboTax Online, you can attach the 1099-B to your return, rather than mail it in. 

Otherwise, you can efile your return, but you'll need to mail the 1099-B in with Form 8453.

Please see the TurboTax Help article When do I need to include my 1099-B with my return? for information and guidance.