Thank you for taking the time to reply. According to the USPS tracking number, it's still in transit to the destination, but arriving late. The problem is, it's been saying that for days, now. It's been in Kansas City for five days, and "departed the destination facility" three days ago. It's a bit nerve-wracking, since I mailed the package on the 16th. I'll try calling the post office Monday morning, and see if it's budged, at all, or if they're finally giving up on it. I'm probably worrying for nothing, but it just seems like it could have WALKED to the IRS, by now.
