As far as I knew it is possible to pay into a pension before 31/Oct this year and have the tax relief allowed for last year. However the paragraph below seems to indicate it could apply up to the online filing date (so 16/Nov for this year). I haven't been able to find anything else on the Revenue website on this so looking to see if anyone can provide something more definite?
"You may pay a once-off or special pension contribution after the end of a tax year but before the following 31 October. If you do, you can choose, on or before 31 October, to have the tax relief for the contributions allowed in the earlier tax year. When you use the Revenue Online Service (ROS), the deadlines for paying contributions and making this choice are extended."
Taken from (can't post the link):
Revenue -> Home -> Jobs and pensions -> Pensions and tax -> 2. Tax relief for pension contributions
"You may pay a once-off or special pension contribution after the end of a tax year but before the following 31 October. If you do, you can choose, on or before 31 October, to have the tax relief for the contributions allowed in the earlier tax year. When you use the Revenue Online Service (ROS), the deadlines for paying contributions and making this choice are extended."
Taken from (can't post the link):
Revenue -> Home -> Jobs and pensions -> Pensions and tax -> 2. Tax relief for pension contributions