Can a tag clock you in and out?
Technically yes, and the technical half is trivial: a tap records an identifier and a time. The difficulty is everywhere else, because a record of when a person arrives and leaves is personal data about an employee, and the rules around that are not something a tag decides.
The easy half
A tag holds an identifier. A phone or a fixed reader recognises it, records the moment, and sends it somewhere. Nothing about that is difficult or expensive.
Either the tag is the person, carried as a card and presented to a reader at the door, or the tag is the place, fixed to a wall and tapped by each person's phone.
The second is cheaper, because the phones already exist. It also means asking people to use their own device for work, which is a decision rather than a detail.
The half that is not technical
A record of when a named person arrives and leaves is personal data about an employee, and in most places it is regulated.
What is required varies by jurisdiction and by the nature of the employment, and the obligations fall on the employer rather than on whoever installs the tags.
The practical consequence for a small deployment: this is a question to settle before any hardware is bought, not afterwards. Retrofitting a rule to a system already collecting is far harder than designing to it.
None of that makes it a bad project. It makes it a project with a non technical half that is larger than the technical one.
What a tap actually proves
That a tag was presented to a reader at a time. Not that a particular person was there, since a card can be carried by somebody else.
For counting hours in a small team who trust one another, that is entirely sufficient and the honesty of the record is the same as it was on paper.
For anything where the record has consequences, understand that the system records presentations of a token and treat disputes accordingly.
A tag also cannot tell you that somebody forgot. Missing taps are the normal failure and the process needs a way to correct them.
Tracking your own time
The version with none of the complications is the one where you are the only subject: a tag on your own desk, a tap when you start and when you stop, going into your own records.
Here the tag genuinely helps, because the reason people abandon time tracking is the friction of starting it, and a tap removes exactly that.
Expect gaps anyway. A tap only records when you remember, and a week with holes in it is the normal outcome rather than a fault.
Frequently asked questions
Is this legal?
Recording when employees arrive and leave is regulated in most places, and the obligations fall on the employer. Settle it before buying anything.
Does a tap prove who was there?
No. It proves a tag was presented. A card can be carried by somebody else, which the system cannot detect.
Should the tag be on the person or the wall?
On the wall is cheaper, since it uses phones that already exist. It also means asking people to use their own devices.
What about tracking my own hours?
That version has none of the complications, and a tap removes the friction that makes people abandon time tracking.