The contract payments are either nominal or fully index-linked to RPI (longer true record than for either CPI or CPIH). The differences between RPI and CPI are explored here and the differences between CPI and CPIH are explored here.

For ILGs, the mark-to-market inflation assumption is explicitly assumed to be the difference between yields on conventional gilts and index-linked gilts. This will generally be different from the inflation used for off-market calculations, the average being 0.65% pa with a standard deviation of 3.60% pa.