Nationwide Building Society has increased the interest rate offered to customers seeking a tax-free savings option for one and two years. The building society has upped the rate it offers on the one and two year fixed rate ISAs, and withdrawn all previous fixed rate ISAs from sale. As of March 19, 2024, the One Year Fixed Rate ISA pays 4.50 per cent AER/tax-free. Meanwhile, the new rate for the Two Year Fixed Rate ISA is now 4.20 per cent AER/tax-free. These rates are available for balances of £1 or more. In January, Nationwide announced a rate of 4.25 per cent AER/tax-free for its One Year Fi…