From 6th April 2016, you can replace money you’ve withdrawn earlier in the tax year from any Nationwide cash ISAs, without impacting your annual ISA allowance as long as you replace it in the same tax year. That means you can take everything out and put it back in again as many times as you like within the same tax year, without counting towards your annual ISA Allowance.
Say you paid £15,240 into your cash ISA at the start of the tax year in April, and then withdrew it all to pay for a new car in July. Then in October, you received a surprise £15,000 bonus. You could pay this back into your ISA with us.