Class 1 structural overview from 6 April 2009: structural changes: secondary NICs
Section 9, SSCBA 92
No changes have been made to the way in which secondary NICs are calculated. However from 6 April 2011 the Secondary Threshold (ST) is no longer aligned with the Primary Threshold (PT).
Secondary NICs are due on all earnings above the Secondary Threshold, see NIM01008, at a single percentage rate