How does a cash ISA work

You can put up to the limit each and every year into an ISA.
The limit is about to be increased to £15K in July.

Ok so even if you put 15k next year in an ISA would that all be tax free including the returns you would gain?

balotelli12's addressed this point, though bear in mind that you can only make use of each tax year's ISA allowance during the year in question - so if you don't invest the full £15k before the end of the tax year (5 April each year), that allowance doesn't carry forward for use in future years.

Money Saving Expert's ISA guide is pretty good at explaining the fundamentals of how they work - you might also like to take a look here: http://www.moneysavingexpert.com/savings/ISA-guide-savings-without-tax

Let us know if you have any other questions about them.

Thanks I only have one question say if I opened an ISA now the ones were you have 120 day notice and put £2k this year would I be able to put £2k the next year again and so on...

There's nothing in the ISA rules that would prevent this, but you should check that the terms and conditions of the account in question (which can include additional restrictions for some accounts) also allow this. I'd expect that this would probably be fine though.

Ok thanks what would happen if you put over £15k in how much tax will you have to pay on the interest

Ok thanks what would happen if you put over £15k in how much tax will you have to pay on the interest

You can't put more into the account.

The difference between the limit and what you try to put in will be returned to you.

Ok so from July the bare maximum you can put is £15k? Can't you have 2 ISAs if you have over 15k

Ok so from July the bare maximum you can put is £15k? Can't you have 2 ISAs if you have over 15k

Ok so from July the bare maximum you can put is £15k? Can't you have 2 ISAs if you have over 15k