[novemberslady]

I mailed my return and they cashed my check within a week!

Can't process a paper return, but they cashed my check too.
The same week they got it.

[texas booster]

The IRS outsources many of their operations.

Texas mails our paper returns and checks to an IRS center in Charlotte NC, that used to be manned by the old NCNB, now BofA after the merger.

Very common - contract a bank to process paper checks and handle tax law themselves.