Per the end of that link it mentions that if a bonus is paid out within 6 months of the end of the year the PAYE/PRSI/USC is due when the salary is actually paid. If it is not paid within 6 months of the year end then it indeed must be accounted for on the P35/p30s of the previous year and interest accrued.
Section 996 TCA 1997
, does not apply to:
(a) emoluments to which Section 984 TCA 1997 applies (i.e. emoluments which are to be taken into account in computing the profits of a trade or profession)
and (b) unpaid remuneration which is paid before:
(i) the date of expiry of six months after the date on which it is deemed to have been paid
or
(ii) in relation to a period of account of more than 12 months, the date of expiry of 18 months from the first day of that period of account if that date of expiry is later than the deemed date of payment.