Your parcel has no idea where it is. There is nothing in the box that knows anything, and nothing on the outside of it broadcasting a position. What your parcel has is a number, printed on the label as a barcode, and what the courier has is a network of scanners that record every time and place that number is seen. When you refresh the tracking page you are not watching a dot move. You are reading a list of sightings.
That single fact explains almost every strange thing tracking does. It explains why the page updates in sudden jumps rather than smoothly, why a parcel can sit in “in transit” limbo for two days and then appear at your door, why “out for delivery” can be true for nine hours, and why the system occasionally loses a parcel completely and then finds it again in Warrington. There is no continuous truth being recorded. There are only the moments when the number passed a machine. Here is what those moments actually are.
The label is the whole story
Look at a Royal Mail or Evri label and you will see more codes than you expect. There is the human readable tracking reference. There is usually a one dimensional barcode, the classic stripes, which encodes that reference. Increasingly there is also a two dimensional code, either a Data Matrix or a QR style square, which can hold far more: sender, service level, destination postcode, weight class and the routing instructions in one small block that survives being scuffed.
Royal Mail also uses a distinctive four state barcode, the row of short vertical bars of differing heights that looks like a heart monitor trace. Each bar has one of four possible shapes, and the sequence encodes the postcode down to a delivery point suffix, which identifies your specific letterbox rather than just your street. Machines can read that pattern at extraordinary speed, which is precisely why it exists.
None of these codes contain a location. They contain an identity. Location comes entirely from where the reading happened.
The first scan happens before the parcel exists
When you order something and the tracking page says the courier is expecting your item, no parcel has moved. The retailer has sent the courier an electronic manifest, a data file that says a box with this number is coming, weighs about this much and is going here. The number is alive in the system before the box is taped shut.
This is the source of one of the great tracking frustrations. A parcel can show as “awaiting collection” for two days while it is in fact sitting on a shelf in a warehouse in Dunstable, or while it is already in a van, because nothing has scanned it since the manifest arrived. The retailer created the label. Nobody has looked at it yet.
Inside the depot, where the reading really happens
The big scans happen at sortation hubs, and they are genuinely impressive places. Parcels are tipped onto belts moving at several metres per second and pass through scanning tunnels: arrays of cameras and lasers arranged to read a barcode on any of the six faces of a box, at any rotation, without a human touching it. Alongside them sit dimensioning units that measure the parcel with light curtains and weigh it on the fly, because volume and weight decide what it costs and which vehicle it fits.
If the barcode is damaged or covered in tape, an optical character recognition system tries to read the printed address instead. If that fails too, the parcel is diverted to a manual station where a person reads it and keys it in. That diversion is often the invisible cause of a day’s delay.
Each successful read pushes an event into the carrier’s database: number, time, site, and often the specific chute. Those events are what the tracking page renders back to you in friendlier language. “Arrived at national hub” is a machine seeing some stripes at half past two in the morning.
Where RFID actually fits
Barcodes have one great weakness: they need line of sight. Something has to see them, which means every parcel must be presented, one at a time, to a scanner. This is where the other technology comes in.
RFID, short for radio frequency identification, is a tag with a tiny chip and a printed metal antenna that answers by radio rather than by being looked at. A reader can interrogate hundreds of tags at once, through cardboard, without any of them being visible or in any particular order. That sounds like the obvious answer to parcel tracking, and yet very few individual parcels carry one.
The reason is money. A printed barcode costs effectively nothing. An RFID tag costs a few pence. Across the 1,347 million parcels Royal Mail handled in the year to March 2025, or the billion plus now moving through Evri Group after its merger with DHL eCommerce UK, a few pence per item is a nine figure line on a spreadsheet for a benefit that a barcode mostly already delivers.
So the tags go on the things that come back. Roll cages, plastic totes, pallets, air freight containers and trailers are tagged, because those assets are reused thousands of times and the cost is spread across every journey. A gate at a depot door reads an entire cage of tagged containers as the forklift drives through, without anyone stopping. Retailers also use RFID heavily inside their own warehouses before the parcel is ever created, which is a story we tell in full in our guide to RFID in logistics from warehouse dock to last mile.
The last mile is a phone in someone’s pocket
Once your parcel is loaded into a van, the entire tracking infrastructure reduces to one device: the driver’s handheld terminal, which these days is usually just a rugged smartphone.
It carries the route, it scans each parcel as it is loaded and again as it is handed over, it takes the photograph on your doorstep, and it reports its own position by satellite as the van moves. When a delivery firm gives you a live map with a van icon and “you are stop 14”, that icon is the driver’s phone, not the parcel. The two are assumed to be in the same place, which is nearly always true and occasionally the source of a spectacular error.
Geofencing is what triggers the polite updates. The system draws an invisible circle around your address, and when the phone enters it the app fires the “arriving in a few minutes” message. Nothing on the parcel is involved at all.
So why does “out for delivery” last nine hours?
Because it is one scan, not a promise. That status is set when the parcel is loaded onto the van at around five in the morning. A busy urban round can carry between 150 and 250 stops. If you are stop 190, you are genuinely out for delivery from dawn, and you will see the van at half past six in the evening.
The time windows carriers show you are predictions from a routing model, updated as the driver progresses. They degrade badly when reality intrudes: a traffic closure, a block of flats with no answer, a driver taking a different sequence to avoid a school run. The prediction was never a commitment, it was an average.
The other classic, “we attempted delivery”, sometimes reflects a genuine knock and sometimes reflects a driver running an hour behind who scanned a card rather than lose the round. Carriers now counter this with photographic proof and timestamped location data, which is why doorstep photos became standard.
Why returns fly through and deliveries crawl
You have probably noticed that a return can be refunded within an hour of you dropping it at a shop, while the original delivery took three days of anxious refreshing. That is not because returns move faster. It is because the retailer has decided to trust the first scan.
When the parcel shop scans your return, that single event is enough for many retailers to release the refund, before the item has been transported, opened, inspected or restocked. They are making a commercial bet that most returns are honest, and that the goodwill of an instant refund is worth more than the fraud it enables. The parcel then travels back through the same slow network as everything else, quietly, while you have already got your money.
Frequently asked questions
Is my parcel being tracked live by GPS?
No. The parcel itself carries no locating device. Live van maps show the position of the driver’s handheld device, and everything else you see is a record of the last time the parcel’s barcode was scanned somewhere.
Why has my tracking not updated for two days?
Because nothing has scanned it. Long gaps usually mean the parcel is in transit between sites, sitting in a queue at a hub, or waiting on a manual station because its label could not be read automatically. The parcel is usually fine, it is simply invisible between sightings.
Why does it say out for delivery all day?
The status is set once, when the parcel is loaded onto the van in the early morning. A single round may hold well over two hundred stops, so being out for delivery at six in the morning and arriving at seven in the evening are perfectly consistent.
Do couriers use RFID on parcels?
Rarely on the individual parcel, because a few pence multiplied by a billion parcels is unaffordable. RFID tags go on the reusable assets instead: cages, totes, pallets and trailers, which can be read in bulk as they pass through depot gateways.
Can a parcel really be lost and then found?
Yes, and it is usually mundane. A parcel that falls behind a chute, gets bagged with the wrong route or has an unreadable label simply stops generating scan events. It has not vanished, it has stopped being seen, and it reappears the moment a human puts it back in front of a scanner.
Why do I get refunded for a return before it arrives?
Because the retailer chooses to act on the drop-off scan rather than wait for the item. It is a calculated commercial risk, taken because fast refunds keep customers buying and the fraud rate is low enough to absorb.
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