The most important rule in the UK constitution is that a Parliament cannot bind future Parliaments. This government can pass whatever laws it likes and future governments can repeal and replace every last one of them.
So this bullshit started off under New Labour with legally binding carbon budgets and Boy George is trying the same stupid trick with the Charter for Budget Responsibility which would legally prevent future governments from spending more than they receive in tax revenue when the economy is growing.
This is so vague as to be a meaningless and reminds us of yet more New Labour bullshit, the Golden Rule. It also reminds us that even though the Tories insist that the economy is recovering/growing, they are spending money like a drunken sailor who knows he is terminally ill and who has just won the lottery while on shore leave.
So the only reason to vote for this - if you could overcome your inner pedant - would be that as soon as it receives Royal Assent, you could have the entire Tory cabinet arrested for breaking the law.
Which raises the next question, does the Charter actually say what the penalties are if a future government does not comply with the law or tries to repeal it..?