Paid application before 6April, still need IHS number?

[dodo2014]

My husband has submitted and fully paid his spouse settlement visa before 6April2015, but has booked appointment on 17April2015. I know there is no requirement to pay IHS charge. But, does he need to register for IHS reference number as the application form and appointment confirmation and e-mail have not mentioned anything on IHS reference number?

Thank you.