alig6 Graham

Completing a n HRP claim form for my 81 year old mum at the moment. Stuck on 1 question re date when her child benefit was first paid. As she can only claim from 1978 onwards and had 3 children, how can she give the exact date the first payment was made as I believe Child Benefit was phased in from 1977 onwards? the question asked for the specific day/date /year of her first payment. Where is this information obtained as I cannot submit the claim form with it missing. Thank you