Does tag orientation matter?
The plane matters and the rotation within it does not. A tag lying flat against the phone reads, and a tag presented edge on collects almost nothing. Turning a tag a quarter turn in its own plane changes nothing at all, which surprises people who expect a keyed alignment.
The two coils must face each other
A tag draws power from the field passing through its loop, and that requires the field lines to cross the plane of the coil.
Hold a tag flat against the back of a phone and the field passes straight through it. Hold it edge on, at ninety degrees, and the field runs along the plane of the coil rather than through it, so almost nothing is collected.
In between, the coupling falls off as the angle grows. A tag tilted moderately still reads, and a tag close to perpendicular does not.
Rotation does not matter
Spin a tag in its own plane and nothing changes. The coil is a closed loop and the field through it is the same at any rotation.
This is worth stating because people expect an alignment, the way a key has one, and search for a correct rotation when a tag misreads. There is none, and time spent there is time not spent on the actual cause.
Slight off centre placement matters more than rotation, since the phone coil is small and the overlap between the two loops is what counts.
The mounting error this causes
Mounting a tag on an edge, a rim or a narrow face, where the natural approach brings the phone in perpendicular to it.
A shelf edge, the lip of a counter, the side of a post: in all of them a person approaches with their phone parallel to the ground while the tag faces sideways. The geometry defeats the tap regardless of tag quality.
The same happens with tags placed on a surface people approach from above but which faces horizontally, such as the front of a machine at waist height.
The fix is to put the tag on the face people present a phone to, which is usually the one they can see comfortably.
Fixing a badly oriented tag
Move it to a face perpendicular to the approach rather than parallel to it. This is almost always possible and it costs one tag.
Where the mounting is fixed, mark the approach. An arrow or a phone symbol showing how to present the device recovers most of the loss, because the problem is that people do not know to turn their phone.
And test by approaching the way a visitor will, not by holding the phone flat against the tag. Testing with a deliberate flat presentation hides exactly this fault, which is why it survives into deployment so often.
Frequently asked questions
Does the tag have a front and a back?
For reading purposes both faces work, since the field passes through the coil either way. On metal tags and metal cards are the exception, because they are built to work from one side.
Should the tag be aligned with the phone's long edge?
No. Rotation in the plane makes no difference, and only the overlap between the two coils matters.
Why does my tag read on a table but not on the wall?
Usually the approach angle changed with the mounting, and sometimes the wall material did. Check both before replacing the tag.
Can a tag be mounted at an angle?
A moderate tilt is tolerable and a steep one is not. Mount it so the natural gesture brings the phone roughly parallel to the tag.