After taking the retirement lump sum (tax free up to €200,000) out of the DC fund, you must use the balance to provide a retirement income- either buy an Annuity or invest in an ARF from which you draw down an income. Any such retirement income plus any State Retirement Pension is potentially liable to Income Tax if it exceeds the threshold- €18,000 for a single person or €36,000 for a couple.
It is arguable that making AVCs is tax effective:
- yes it will increase your tax free lump sum , probably by 25% of the AVC fund
- yes you will get tax relief on the contributions
- but any additional pension income will be potentially taxable in retirement
So if you will get tax relief on the AVCs at top rate - 40% - but any additional pension income was going to be below the threshold or only taxable at the lower rate of 20%, then it may be a tax effective strategy. However if you will still be in the top tax rate after retiring, then it may not make much sense since your marginal tax rate on the additional income in retirement will be 40% + USC ( circa 44% total).