I have researched this and this is how this happens: Normally when you hand someone a check, it is scanned and becomes an image check which is settled through the check 21 system back to your bank. But when you write a check to the IRS it is converted to an ACH transfer because this is cheaper to process. The Federal Reserve has a structure called the Debit Gateway where this is occurs and there is also a system that checks for duplicate transactions to prevent exactly what happened to me - a withdrawl from my account first as a image check (check21) and then later again as a ACH. The IRS has nothing to do with all this - they just see what the Federal Reserve reports to the,m. The only reason I wrote a check was because my return kept getting spit back due to an AGI problem when I tried to do it electronically. Moral of the story, avoid writing a check because it adds extra steps in processing and increases the chance of something going wrong.
