When i was in the cellular industry, specifically tmobile actually, if customers didnt pay their bill in 4-5 months after activating with your store, the commission tmobile pays out gets taken back. For the businesses that are under CPD, which is a master dealer, they are the ones who suffer the loss realistically, but CPD doesnt lose the money for the phones since the businesses under them already paid for them.
Since "bad debt" is is a loss that you cant get back, it is most likely chargebacks that you see on the "bad debt" income report. It seems to vary from year to year, but is still high. The higher the revenues go, the higher that will most likely be.
Im not 100% sure if that is the case, but I couldnt find anywhere else where chargebacks would be in the loss column besides the "bad debt" section. Technically it isnt even a loss to the master dealer, but it is able to be written off, and you can bet they are writing that loss off for tax purposes.