Can I use an old PCR test?

[IWasBornInAThunderstorm]

Had to do PCR tests a couple of weeks ago and in the hazy confusion of sorting it out we have ended up with a spare test. Can I use this next time someone needs a test or do I have to order another one?

I used an old one I had ordered when my child had covid and it was fine. Just remember to register it before you send it off

Thank you!