NIM01230 - Class 1 structural overview from 6 April 2009: structural changes: secondary NICs
Section 9 of the Social Security Contributions and Benefits Act 1992 (SSCBA 1992)
No changes have been made to the way in which secondary NICs are calculated. However from 6 April 2011 the Secondary Threshold is no longer aligned with the Primary Threshold.
Secondary NICs are due on all earnings above the Secondary Threshold at a single percentage rate.