Age points are often specified in certain civil service standard grades. That is, anyone (usually school-leavers) under a certain age are paid on a point appropriate to their age. Generally though, the age point thing really just comes into being for those who join straight from school or college where they may be under 21, so the first point or two on a scale might be age 18 or 19 or so. Or may even start at age 23 or so.
If you join a grade and the first point is for example age 23 (and you are, say 35) then you generally start at that point (the age 23 or over point). None of the points on the remainder of your incremental salary scale have anything to do with your age - just the first one. You then progress on through the various increments each year until you reach the maximum of the scale.
The only exception to the above is where you are an existing Civil Servant and get promoted to a higher grade but that's another matter.
When any Civil Servant reaches the maximum of their scale, they remain on that point for a few years (usually 3) and then receive a long-service increment. After remaining on that 1st long-service increment for a further period (usually another 3 years) you will progress to the 2nd long-service increment. Apart then from increases in national pay agreements etc. you will not receive further pay increases until you are either promoted to a higher grade (or you may be moved to a higher grade).
It's worth bearing in mind that annual pay increments on salary scales are not awarded without reviewing performance. Failure to achieve the appropriate standards means you will not receive your increment.
Civil Service pay circulars (and all other circulars) are published on the Dept. Finance website and you can review them here:
http://www.finance.gov.ie/ViewDoc.asp?DocId=-1&CatID=28&m=c
Specific informaton relating to the actual pay or age points on general service Civil Service Grades is available from the Public Appointments Commission ()