@zed1011 heres what it means they have processed and something didnt add up you are being put under review
We’re reviewing your tax return.
We sent you this notice because we’re reviewing your tax return to verify:
The income you reported on your return
The income tax withholding amounts you reported on your return
The claims for tax credits you made on your return
The withholding claimed on your Social Security benefits
The household help you claimed
The Schedule C income you claimed
We’re holding your refund until we finish our review.
So its a type of audit not a major audit but they aresending to diffrent department to investigate