(1) Subject to this section, the amount which may be deducted or set off in any year in respect of contributions made by an individual to one or more PRSA products, hereafter in this section referred to as the maximum allowable contribution, shall not be more than -
(a) in the case of an individual who at any time during the year of assessment was of the age 30 years or over but had not attained the age of 40 years, 20 per cent,
(b) in the case of an individual who at any time during the year of assessment was of the age 40 years or over but had not attained the age of 50 years, 25 per cent,
(c) in the case of an individual who at any time during the year of assessment was of the age of 50 years or over but had not attained the age of 55 years or who for the year of assessment was a specified individual, 30 per cent,
(d) in the case of an individual who at any time during the year of assessment was of the age of 55 years or over but had not attained the age of 60 years, 35 per cent,
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