If you make a cash subscription to your IFISA account, the amount subscribed will use part of your ISA allowance, even if you do not use this subscription to make an investment.
If you do not use up your ISA allowance, it will not be carried over to the next year.
If you open an IFISA, but do not subscribe any funds to it over the tax year, then it will be a considered a ‘break year’. This means that, because no subscriptions were made during the tax year, you will have to make a new ISA declaration next time you seek to subscribe in the IFISA.
PLEASE REMEMBER, REGARDLESS OF THE TAX BENEFITS, CAPITAL IS AT RISK
Whether investments are held within a IFISA or in a general account, they are not covered by the FSCS; the government backed deposit insurance scheme that protects bank deposits including Cash ISAs.