My client has just realised she would have been entitled to RP had she claimed it since 1991.

She'll now be making her claim but we're a little unsure how she will benefit from deferment provisions.

She had racked up her entitlement to the full additional 37% under the rules that applied before April 2005, but does she benefit from just that provision or from just the new provisions (0.2% extra per week for each week of deferment after April 2005)or from both?

nope - the more generous rules for deferral (the higher percentage accrual rate, the option of a lump sum and the abolition of the five-year limit) only apply from April 2005

she'll get the full 37.5% increase to her RP for the period before, plus the option of a further increase to her RP or a lump sum of all the RP she's failed to claim since April 2005 (plus interest). The lump sum is taxable, but ignored forever for all means-tested benefits (which might be handy)

what I don't know is how they would calculate the lump sum if she opts for it -- would it include the 37.5% increase ?

don't forget, no increase for deferral in she received other benefits (or anyone else claimed for her)