They don't need your permission. However, it is strange that they never took an excess from you. Did you not think, within that 8 month period, to contact your insurer for an update? They can't always be relied upon to keep you in 'the loop'. How much NCB did you have prior to the accident? I'm guessing not much, which has why it has gone down to zero - but worth re checking with your old insurer. There may be a NCB matrix in your old policy document if you still have it.