Redwood,
I am presuming you are a clerical officer i.e. an indoor staff member. One option (if possible) to top up your pension would be to return to full-time hours. This would increase your service and aid your superannuation entitlements.
In answer to your question your HR Dept. are correct in stating you cannot purchase years periodically i.e. weekly/fortnightly etc until retirement, payments would have to have commenced at the latest at 63. They are incorrect if they have advised that you cannot purchase service by lump sum i.e. one off payment, at any time prior to retirement. Purchasing notional service is expensive, to buy one year for pension purposes would cost approximately 25% (depending on your age at payment and your PRSI class) of your gross fulltime salary i.e. €39,556. You would get tax relief on the payment.
AVCs are outside the Local Government Superannuation Scheme, therefore you need to see a financial advisor to discuss. Ask about a "last minute AVC", which if I understand correctly basically means you put in a lump sum into an AVC prior to retirement receive the tax relief on it and then can get lump sum back after retirement. However it is more beneficial to those on the higher rate of tax.
A few questions that you would want to make sure you have checked out before retirement:
1. has all your service with all public sector/ semi state bodies been taken into account.
2. If you received a marriage gratuity (if female) in the past have you examined paying it back to get the benefit of service prior to gratuity.
3. You have CS and LA service were they in different PRSI classes i.e. D class or A class. If for example you worked with the CS from 1983 to 1992 you would have 9 years at D class, this would be one pension calculation. If you left the public sector and returned in 1999 job sharing with local authority you would have a separate pension calculation at A class.
Hope the above is of some help,
E