To expect ex to pay half if he offered to pay half

[CardiffUniversityNetballTeam]

DS back to school this week. I spoke to ex earlier in the week about school dinners. I said I was thinking about paying for a terms worth in advance to save having to make sure I always had change in the house to pay for them daily. He said he thought that was a good idea, and I asked if he was alright to pay half. He said yes and also asked if he owed me anything for replacement uniform. So far, so civilised.
Fast forward to last night and he comes round here to drop off some of DS things for the weekend and collect his mail.
I ask about the dinner money. He says he's really sorry but he can't afford to pay me back right now as he's skint. I asked when he gets paid again, he says in three weeks, but he might not be able to give it to me then either as he needs to buy a new van!
AIBU to think he should never have bloody offered to pay half if he knew he couldn't afford to pay me back? I'm kicking myself now for falling for this as he totally has form for being a complete cunt a bit flaky.

If you split expenses 50/50 then he is BU.

If he pays child support as well as extras then you are BUT as he already pays what's due plus more.

Lesson learnt, don't spend money you can't afford.

We have shared residency, he has DS 3/7 and doesn't pay any maintenance.
I can afford it, I wouldn't have paid it if I couldn't. I'm just annoyed he said he'd pay, when he must have known he couldn't.
I guess it's these kind of reasons that he's my ex.

Why don't you have something formal in place regarding costs? I would get this sorted ASAP.

Also, why is his mail going to your house?

I know the feeling Cardiff. When my now late teens were in Primary school eldest was going on a school trip, I think it cost about £30. I couldn't afford it as I had 3 small kids so i asked ex to go half's with me. He wanted a letter from the school spelling out - 1 - how much the trip was costing 2- what the education value of the trip was 3 - a breakdown itinerary. Of the school was really going to provide that

But my ex hardly ever saw them (his choice) and apart from his maintenance which he grudgingly paid - and way below CSA levels - he never bought a single thing for them. Not one thing. No clothes, uniforms anything.

My mum paid the extra £15 in the end. I have never asked the tight fisted shit for anything ever again.

There isn't anything formal in place regarding money because we have been getting on okay informally so far. I don't want to stir up a hornets nest when I don't have to. I wish he'd just said, "I can't afford to pay half right now," when I first proposed the idea.
His mail is still coming here as he is too disorganised to set up a redirection. For the same reason, there is still a big heap of his stuff in the corner of the dining room, in spite of the fact that we broke up nearly a year ago.

VodkaJelly sounds like your ex is/was a bit of a shit. At least mine sees DS a lot.

If your claiming any benefits, tax credits as a single parent get his mail redirected immediately. Currently DWP and HMRC could say you are still together. It's not about being arsey

Please get his mail redirected asap.
If (god forbid) you ever needed to claim benefits, it would be assumed you were living together.

Thanks, I'm not currently receiving any benefits, but I will get his mail re-directed so if I need to in future there is no question that I live on my own.