NIM01130 - Class 1 Structural Overview from 6 April 2003: Structural changes: Secondary NICs
Section 9 of the Social Security Contributions and Benefits Act 1992 (SSCBA 1992)
Although as part of the structural changes to Class 1 NICs from 6 April 2003, the secondary percentage was raised by 1%, no changes have been made to the way in which secondary NICs are calculated.
Secondary NICs are due on all earnings above the Secondary Threshold, see NIM01008, at a single percentage rate.