These letters are issued if there has been any sort of questionable activity or sort of fraud involving your social security number or identity. It is intended to protect you from further issues.
If you have not filed your 2020 tax return as you are waiting on the letter, the IRS will use the latest tax return on file to make your third stimulus payment.
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This doesn’t quite answer my question, I’m wanting to know if me still having to verify my identity cause issues with me getting the third stimulus payment? Will it be delayed like my tax refund is? Or will the send it anyways?