Had a chat with the tax office. I am informed that National Insurance should NOT be paid on TA pay if you are in (main) employment and you are paid above the Upper Earnings Limit (UEL - not sure of the exact figure). In this case your 'second employer' (ie the Army Pay Office) should seek a deferment from paying NI. As an 'employee' you cant arrange this yourself! Has anyone achieved this yet with APO and what about reclaiming the overpayments?