Age Allowance in IRC is automatically included as part of the IRC rating calculation. It is based on the mean of Series Date and Age Date and starts when that mean figure is 3 years old.
Series Date 1995
Age Date 2003
'IRC Age' for age allowance = 1999. In 2017* age allowance started for boats with 'IRC Age' of 2014 or older, so for this example it would get 15 years allowance (2014-1999).
Series Date 2007
Age Date 2007
'IRC Age' for age allowance = 2007.
The amount of age allowance is small, not even 0.001 per year, and is just one aspect of all the many changes that take place in the formula each year. Hence ratings do not automatically reduce each year because the boat is older, but the age is taken into account in the TCC calculation.
Maximum age allowance is reached at 20 years.
*This article was written in 2017