Even more fun.... I was audited by the IRS a few years ago and they asked for documentation 2-1/2 years past the filing date. I sent them paperwork as requested. They sent me letter after letter saying they were over worked and needed 45 additional days. Come July 27 of the following year (3 years 3 months form the filing date), they sent me a bill. I objected to the bill because they had negated my claim of head of household. They said sorry charlie, you can't make changes to your tax return after 3 years... but THEY DID. They said it was their rule and it only applied to the tax payer, not to them. seriously.
Also, I sent them a check once. It was delivered on thier requested due date. I sent it by USPS and it was post marked two days prior. They charged me a late fee. When I showed them their policy about USPS vs FEDEX/UPS and the postmark being a legal date, they said that didn't apply. The date used was when the check cleared the bank.
They don't even follow their own rules.