Interested

In Box 4 ("In reply to your S040 of..."), for "period under our legislation", does HMRC answer on the basis of the dates someone was covered by the NHS ie had a valid NHS number or on the basis of the dates for which NICs were paid? Similarly, in Box 5 (" Insurance period"), does HMRC enter the dates someone was covered by the NHS ie had a valid NHS number or the dates for which NICs were paid?