that answer is perhaps not helpful
any one can pay in
any of the named joint holders can with draw
confusion reigns over this
you pay in £10 000 either one of you can take it out
BUT it is "traceable" - it is yours and is part of your estate (*)
even my nephew got that one wrong (egged on I regret by the bank who were advising in their own interest and not in his)
when you die - it is operable by him and is not frozen as all your singly held assets are until probate is granted
I regard this as a big big advantage
your money in it is part of your estate and is taxable as such
Your son pretends it isnt ?
oh no no! PP puts hand to face and looks like the scream by Edward Munch
The ownership bit is settled by a case called Re Northall
and is well covered by this
https://www.fridaysmove.com/articles/joint-bank-accounts-recent-case-re-northall-deceased-2010-15832
[it is pretty straighforward: Mrs Northall paid in. she died. younger Northall said "mine all mine -tax free!" and the tax judges said "oh come on you're joking, it is part of her estate and taxable, duurrrrr"