To claim overtime as my new boss now wants me to "make up" some lost time.

[Prevalence]

I've worked at company for around 9 years. No issues, work done etc on a salary.
New boss arrived in January. A couple of weeks ago, I said I'll be in late because of dentist at 9, so will be in around 9:45. Just a heads up.
He says "that's fine. When will you make that time back up?
Me: "what do you mean?"
Boss: " the 45 minutes. When will you make that up?"
Me: "errr... I won't?"
Boss: "you have to. All time off needs to be made up"
Me: right, in that case then, all extra hours need to be time off in lieu of overtime then?
Boss: sounds fair.
Me: ok, when did this new policy start please?
Boss: Jan 1.
Me: ok. I'll submit my overtime then, I'll make up the 45 minutes when it's paid.
Boss: sure thing

Got him to email to confirm.

As soon as it came in I submitted 46 hours overtime, to be paid at x1.5 🤣🤣

He blew a gasket, complaining it would come from his budget etc I said "but that's the policy. Feel free to deduct 45 minutes,and then I won't make up the time.

I will now be working 9-5, no overtime, nothing!

Tbh I don't think either you or the manager have handled this well. I also work in an industry where people generally do more than their required hours and no one cares that you've got to go to the dentist or a school play as it all evens out and no one clock watches. But as a manager it helps me if the company has a rule about making up hours as it enables me to have a conversation with the pisstakers who always start late or finish early and then complain about the workload. Paid overtime is completely different and has to be approved in advance, you can't just decide to work extra hours and get paid for it.

He could have been more diplomatic. You could have just said you've already made the time up as you've worked an extra 20 hours. He's lost your goodwill, you've lost your flexibility. Not great.

Jobsworth!

Also read the thread. The boss agreed she could submit it!

@Prevalence well done!

I'm surprised you didn't out in your paid overtime hours before though!

If this is the workplace culture, then OP would do very well to start job hunting immediately anyway. Who in their right mind would hang around and put up with rubbish like that? (Assuming they had any other option).