Hi there,Be very careful.. I was in same boat in 2005, filled in form 12 for 2004 and was told in 2006 that it should be form 11E instead for 2005 and 2004 returns even though in 2005 they took the stuff form me on that form anyway!
I have since back and forward to tax office on the phone and have filled out 11E for 2005's return. I am also PAYE and have house rented out.Just check with your local office first as it really pays to get to know someone there who can help, are you dublin based?? My office in Dun Laoghaire/rathdown and they are very helpful.
I since got tax bill for €4500 for 2005 but it was wrong without be knowing as I'm not good with figures (was not my fault but it seems that TAx office frequently dont give you correct allowance etc) and they looked over it all and reduced it to €25, it really pays to do it all now before submitting.
I followed the example in the booklet they can send you about deductions, worth a look too.
Hope this helps