redundancy and date actually paid

Hi all

Hoping someone can shed some light on a problem for a newbie!? :

If an individual has a compromise agreement as parf of their redundancy deal and its dated 4th April, if any payment for redundancy is made say around the 20th April, can the ex-employer just bring that payment into the 2011/12 tax year and adjust the P60 - claiming "it was processed in mth 12 therefore its in 2011/12"

I thought salary and such related payments were deteremined by a "paid" basis and you can't just allocate this based on when you "processed" payments

Does the Compromise agreement being dated beginning of April mean the ex-employer is bound to make the payment and therefore its "deemed" to made in 2011/12?

thks

Smithie