Probationary period after gap year

[Justpassingtime1]

I was working there 2 years then took a gap year.
I have returned to the same place but am on probationary period
again.
Do they have to do this?

They don’t have to, no. No employer has to have a probationary period. But they can. Are you in a different role? Is your service being considered continuous or are you in effect starting again?

Was it a sabbatical or did you resign & rejoin?

Did your employment end before the gap year? P45? Or continuous employment?

Did you employment end or was it a career break, where you keep service accrued? If a probationary period is normal for new starters it can be applied to you if you are reemployed.