AIBU to take my son's phone after he stole £20?

[Summerishere123]

DS13 has stolen £20. I know this because I counted out the cash for a holiday yesterday. I checked it twice and DH checked it. He then put it in the cupboard. We have gone to get it out today and £20 is missing.
I know he has had a few £1 here and there that he has found around the house and have often turned a blind eye. He gets £4 a week spending money and I have told him several times I will up it if he does chores but he wont.
DH says we should ground him for a week and take his phone. I think taking his phone when he is travelling to and from school will cause us more hassle than him but think he should have it taken when he gets in from school and returned in the mornings. Is this fair? To be honest I feel bad because he has always taken bits here and there which we knew, but did nothing about.

He has the option to get more if he does his chores. He refuses. Tbh, he’s lucky to get £4 per week. I would have got nothing if I hadn’t done my chores.

When I was a kid (1950s) chores were very firmly linked to money. Each job had a price and if I neglected to do them all I was short on pocket money that week. My mother argued that when I began work if I didnt do a full day I would not get paid for the time I took off. Fair enough. So I dont believe in givng kids money. Rather in giving them the opportunity to earn it.

With regard to the missing £20 I would be having a frank talk with my son to hear his "story" before I decided on a punishment.

When I was a young woman living at home money disappeared from my bedroom drawer in a way that only my mother or sister could have taken it. I never found out who. Strangely enough it was the exact amount of money my mother has asked me to "give" her because my sister needed new shoes. It created a horrible atmosphere for months because I made a point of always keeping my bag with me after that - even when I slept. That was probably punishment enough for whoever had stolen it.

4 pounds a week? I’d have took 20 pound too.
and by the way, your husband “worrying there won’t be enough” whilst having a wad of cash in the house for a holiday, is actually a form of financial control.

So, you asked your son to go to the shop and pick up a few items for you but you didn’t give him any money to pay with.
When he came back from the shop with the shopping how did you think he had paid for it. ?
You now know that he had taken the £20 and gave you the shopping but kept back £5 from the change for himself.
I ask you again-how did you expect him to pay for the shopping?