A biometric time clock solves exactly one problem, one person clocking in for another, and takes on a set of obligations that outlast the hardware. The technology question is small and the governance question is large, which is the reverse of how these are usually sold. Work out whether you may hold the data before comparing sensors.
What it fixes and what it does not
It fixes buddy punching, which is the only thing it fixes. It does not make the recorded times more accurate, it does not reduce missed punches, and it tends to increase the number of exceptions a supervisor handles in the first months while enrolment settles. If you have no evidence of covering for one another, the business case is thin.
The duties that arrive with it
Notice and consent in writing, a lawful basis you can state, a retention schedule, a deletion process you can evidence, and a position on who else receives the data including the vendor. Biometric data is separately regulated in several US states and treated as special category data in the UK, and the duties fall on the employer rather than on the vendor who sold the device.
Plan the refusal before rollout
Somebody will decline and somebody's finger will not read. Decide the alternative, whether a code or a supervisor punch, before the device is on the wall rather than inventing it at the door on the first morning. An alternative that is visibly a punishment is not a real alternative and will produce a grievance instead of a record.
Questions people ask about biometric time clock
Can an employee refuse?
In practice you need a workable alternative, and in several places consent that is not freely given is not consent. Plan the alternative as part of the rollout.
Is a stored template the same as a fingerprint?
No, and it is still biometric data. Treating a template as an ordinary number is where employers get into difficulty.
What happens when somebody leaves?
Their template should be deleted on a defined schedule and you should be able to show that it was. Ask how deletion is evidenced before buying.