Since prepared tax returns list the address of the firm preparing it, going after out of state tax preparers is low hanging fruit.
I always celebrate whenever one of my clients moves out of CA.
I responded to a CP 2000 related to TY 2019 which the IRS mailed in November 2021.
So far we have received a letter from the IRS dated April 30, 2022 saying that they needed 90 days more time.
This was related to a tax return Form 1040 that was efiled back in February 2020 over 3 years ago.
So far still waiting