My Dad expects me to help him at his work during the summer holidays

I don't think adult children get to just pay rent and that's that. It's up to their parents what contribution they want.

My parents did not want rent, because they didn't need the money, they wanted me to help out with various household things. Including covering the family business so that my dad could have a break.

I really don't see the big deal about that. When I no longer wanted to live as a household with my parents, I left.

I suppose as you’re supply, you are unemployed until September, but if you can afford that then it’s fine. If he was concerned about your finances, he wouldn’t be telling you to work for free. If you wanted a job over summer, you would want paid. What type of work is he asking you to do?

Minority voice here. I think you are being unreasonable. If he expected you to work full time or even most of the time, I would agree with you. But two days a week, when you're living in their home, guessing you have food, laundry, cleaning and other household functions done for you, well would it kill you to help him out? If you feel controlled, it's time to move on from parent living to getting your own place so you can adult for real.

Not unreasonable of him to ask, unreasonable not to pay you.

Call his bluff and get another temporary job.

Ask him to waive your rent while you are working for him?
He can’t possibly think it’s acceptable for you to work for him for nothing!

Supply teachers don't.

She mentions in her OP that she’s been doing supply teaching work (i.e. she’s not under contract and isn’t being paid through the holidays).

Time to move out.

I sold I don't ask a lot of him, but if OP was paying a lot towards the upkeep of her home, I think she'd have mentioned it.

As you have ASD I would have thought the summer holidays were your time to recover from being peopled out. My Dd has just come out of 2 years of ASD burnout. She would need that time.

Also as a teacher, l always had work to do in the holidays. Tell your dad that.

You'd also hope that a teacher was assertive enough to push back on this. If the OP isn't confident enough to talk to her dad about this, how well does she deal with keeping 30 school pupils in line?

OP for a start, you're entitled to statutory holiday for around half the school holidays. So for a lot of them, you're not unemployed, you're on annual leave.

Plus wouldn't you need to be doing some CPD, applying for permanent teaching posts, looking for a contract for next year? Might you also be looking to go away on holiday?

But unless perhaps his business is really struggling and he needs an extra pair of hands, or you're benefitting by living very cheaply with your parents, there's no justification for him to expect you to work for free, so he either pays you or you don't do it.

Also teachers do get paid for the holidays. I suspect OP has a low paid support staff job and isn't paying much rent at all.

In which case, OP is still only responsible for 1/3 of that and there is nothing to suggest she is not doing that already

No. She could easily disabuse us if she felt like it. It’s just interesting that her dad expects a contribution in lieu if she’s already financially contributing and that the OP didn’t move out years ago if he’s such a pita and she gets no financial benefit from being there.

How's the family business financing her lifestyle? She is working, she is being paid a salary which is financing her lifestyle. We have no idea how much rent she is paying to her parents. She may well be financing their lifestyle.
Does your son do a few full days of work per week doing your IT or just a few quick tasks here and there? Because that would make a difference in whether or not he should be compensated.

Is it something like a family farm you will inherit one day?

Autistic parents can be real control freaks, move away as soon as you can. Until then, tell him if he wants to hire you he has to pay you your going rate or you will report him to HMRC.

Don't get into a discussion with him in which he tells you how you feel and what you think and you struggle to argue against him. Try:
"no, I won't be doing that, because I don't want to"
"we've discussed this before and I don't have anything to add"
"please stop talking about this, you are making me unhappy"
"I won't have time because I'll be flat-hunting"

In which case, OP is still only responsible for 1/3 of that and there is nothing to suggest she is not doing that already.

Her parents aren't paying "market rent"

They may well be paying market rent.

What is the compensation package? You can tell him you will get him an answer once you see the details of the benefits involved.

I can't believe the OP is a teacher either. The post and articulation would suggest a teenager has written it.

As a teen, not paying rent, I used to help Dad out in the school holidays - and got paid.
But I was only asked when they were desperate for an extra pair of hands.

You definitely need to "book" some holiday. And seriously consider moving out.

She doesn't, but the pay off is she's expected to give a few days a year to the family business, that is financing her lifestyle.

My son acts as IT support for my business. TBF I don't ask much if him, but I'd be mightily unimpressed if wanted paying, when he has it so cushy here.

Even if you were unemployed, which you're not, why would that justify having to work for your dad, or anyone for free? Ridiculous.
If he wants you to work he can pay you a wage like anyone else. You're not his slave.
If I were you I'd try and move out ASAP. Your dad is clearly overbearing and not very helpful.
Could you afford a flat share with a mate? Or if not then just with randoms, it's better than being bugged by your dad all day long.

If you won't:

• confront him and say no because the holidays are to recharge and prepare for next academic year and he will get his rent; or
• move out

then lie through your teeth. Say the holidays are not actual holidays for staff and you need to prepare for next year's curriculum and classes.

I'm not a teacher so sorry if the terminology is wrong.