Are combined NFC and RFID tags useful?
When one system counts items in bulk at a distance and people also need to tap them with a phone, yes. Two antennas in one label are larger and dearer than either alone, and cheaper than applying, aligning and tracking two separate labels on every item.
What is combined
Two independent tags sharing one label body. An NFC chip with its own antenna operating at the usual frequency, and a UHF chip with a completely different antenna operating far higher.
They do not talk to each other. Each is read by its own kind of reader, each has its own identifier, and writing to one changes nothing about the other.
The label is a packaging convenience, not a technical merger. Understanding that prevents most of the confusion around these products.
Why anyone wants both
Because the two technologies answer different questions and a single item can need both answers.
UHF reads many items at once from metres away, which is what makes stocktaking and gate reading possible. It needs a dedicated reader, and no phone has one.
NFC reads one item at contact range, and every modern phone is a reader. That is what lets a member of staff, a customer or an inspector interact with a specific item without special equipment.
An asset that is counted in bulk by a warehouse system and also consulted individually by people with phones genuinely needs both, and that combination is more common than it sounds.
What it costs
Size. Two antennas need room, and the UHF antenna has a shape driven by its own frequency. Combined labels are larger than either alone.
Price. Two chips, two antennas, more complex manufacture.
Choice. Far fewer form factors, substrates and adhesives are available than for either technology on its own, so the physical requirements may not be satisfiable.
And two identifiers to reconcile. Your system has to know that this UHF identifier and this NFC identifier are the same object, which is a data problem rather than a hardware one, and it is the part usually underestimated.
When two tags are better
When the physical requirements differ. If the UHF tag needs to be on the outside of a crate and the NFC tag on the item inside, one label cannot be in two places.
When only some items need both. Buying combined labels for everything to serve a minority is more expensive than two products.
When the available combined products do not meet the substrate, temperature or surface requirement, which happens often given the narrow range.
And when the two systems will never need to agree. Separate tags keep the projects independent, which has its own value.
Where you do apply two separate tags, keep them apart on the object. They operate at different frequencies and do not interfere the way two NFC tags do, and separation still makes each easier to aim at.
Frequently asked questions
Do the two chips interfere with each other?
They work at very different frequencies, so each reader sees only its own tag. The design work is in fitting two antennas, not in avoiding interference.
Can my phone read the UHF part?
No. Phones have no UHF reader, which is exactly why the NFC half is there.
Is one identifier derived from the other?
No, they are independent. Linking them is your system's job, and it is the part of these projects that is usually underestimated.
Are combined tags widely available?
Far less widely than either technology alone, and in fewer substrates and form factors. Check availability against your physical requirements early.