A tolling back office is the part of an electronic tolling system that matches each passage under a gantry to an account, sends the bills, and chases unpaid tolls for the toll-road operator. A gantry is the frame above the road that holds the readers and cameras. At the gantry, a vehicle is read at full speed. The back office works out who owes the toll.
For every passage, the back office gets the time, the lane and the tag number or the number plate. It looks for an account. If the account has a balance, it deducts the toll. If the vehicle has no account, it identifies the owner from the number plate through the government's vehicle registration records, sends a bill by SMS, and waits for payment. In India, the owner must pay within 72 hours, or the amount doubles. If it is still unpaid after 15 days, it is recorded against the vehicle in the government's registration records. Until the owner pays, some vehicle services can be refused. On a national highway toll plaza with booths, a vehicle with no valid FASTag pays 1.25 times the toll by UPI. Cash is no longer accepted there. The back office matters most where there are no booths to stop it.
It is a large system. A busy road can record hundreds of thousands of passages a day, and each one must be matched correctly, because a mistake means charging the wrong person. So the back office also handles complaints, refunds and disputes.
Say a car owner in Mysuru gets two SMS messages for one passage on the same morning, each deducting ₹115. She complains through the app. The back office looks at the record and finds that two readers at the gantry read her tag within five seconds. A rule says that two reads of one tag at one gantry within a short time are one passage. The system reverses one charge and credits ₹115 back to her prepaid balance.
In some countries, overdue bills go through debt collection software, the same kind of software that banks use. The readers it depends on are described in electronic tolling, which uses RFID and automatic number plate recognition. The wider scene is fare collection and tolling.