Biometric attendance replaces a card with a part of the person. That solves badge sharing and, in UK law, moves the data into a more protected category with a higher bar for using it at all.
The legal bar is higher than convenience
Biometric data used to identify someone is special category data, and processing it needs both a lawful basis and a separate condition. Consent is difficult to rely on at work because the power imbalance makes it hard to show it was freely given, which is precisely why a genuine alternative for anyone who declines is not a nicety but part of making the arrangement lawful.
Do the assessment before you buy, not after
Introducing biometric monitoring is the sort of processing the ICO expects to be assessed in advance. The assessment asks what you are collecting, why a less intrusive option will not do, who can see it, how long it is kept and how it is deleted. Doing it before purchase often changes the specification, which is the point; doing it afterwards is a document justifying a decision already made.
Templates, storage and deletion are contract questions
Ask whether the device stores a mathematical template or an image, whether templates stay on the device or go to a server, where that server is, and what happens to a leaver's template and when. Get the answers in writing before signing, because they are the questions you will be asked by a worried employee and, if it goes wrong, by a regulator.
Test the rejection rate on your own workforce
Published accuracy figures come from controlled evaluations with cooperative subjects and clean sensors. A working kitchen, a cold yard or a workshop produces different numbers. Run a fortnight with real staff, count refused reads per hundred punches, and make sure the fallback route is in place before the device becomes the only way to clock in.
Questions people ask about biometric attendance
Is consent enough to justify it?
Rarely on its own at work, because consent must be freely given. A workable alternative and a documented assessment matter more.
Is a template safer than an image?
It is less directly identifiable, but it is still biometric data and still special category. It does not remove the duties.
What has to happen when someone leaves?
Their template should be deleted on a defined schedule, and you should be able to show that it was.