after 3 years, you should still save a copy of your 1040 and a cancelled check or copy of refund check.
It proves you filed. They cannot audit for errors after that point, but you have to prove you filed.
Please tell me your a tax attorney. My garage isn’t nearly large enough.
I got a letter from the IRS a few years back, claiming that our business return from 7 years prior had not been filed. I found our old copy,and sent it in, along with proof of certified mailing. They sent a letter back admitting they had lost the return,and demanding that we sign and date our copy as the original. Then, they claimed that return was filed as an scorp without proof of scorp status granted. I had to go back to returns over 10 years past that to prove we had been approved. My lesson: save everything, forever.