The personal allowance is calculated each tax year beginning on 6th April. In 2014/15 your total tax-free savings allowance is £11,880.
You are entitled to save the entire amount of £11,880 in a stocks and shares ISA or if you wish you can split it between a cash ISA and a stocks and shares ISA.
The maximum savings limit in a cash ISA is £5,940.
You'll need to make the most of your full allowance by the end of each financial year - although your savings will continue year to year, your personal allowance cannot be carried over.
For example, if you still have £1,000 left of your personal allowance from the current financial year, this does not mean you will be able to save £12,880 in 2014/15 - any remaining allowance will be lost, so make the most of it if you can.