I assume from your post that you are working in the Public or Civil Service.
Cornmarket operate AVC funds for many such groups (through Union agreements). The advantage they seem to offer is that contributions under their schemes generally benefit from tax-relief through the “net pay system “. Otherwise you have to make a tax return at the end of the tax year to reclaim the tax relief.
In the case of “last minute AVCs” you can use Cornmarket, but alternatively you could establish a “stand-alone PRSA AVC” . A number of Insurance providers offer such products. You may or may not get tax relief immediately (if that’s important), but you will get the relief eventually.
everybody retiring (yes , Dept of Justice) seems to be using them , giving certain amount of money (Revenue limits) its "Invested"
you get the money back , with the tax benefit , on top.
In the AVC is being “invested” for only a short period, then you don’t need to take any investment risk, so go for a Cash Fund. If the total AVC fund is going to be used to augment your tax-free lump sum up to the Revenue max, then the tax-relief is your investment return.
So in effect your can turn 60% (100% less 40% tax relief) into 100% over a short period of time.