I've listed some of the main tax credits available below. There are many others, of course, but you should make sure that you are claiming all available to you. And, don't forget, you can also still make a back-claim for the previous 4 years too.
Personal credit
This credit is available to everyone resident in Ireland. The tax credit available is €1,650 for a single person and €3,300 for a married couple per year. This credit will cover any tax on any income up to €8,250 and €16,500 respectively.
PAYE credit
If you work for someone else, who is not a relation, you are also entitled to a further tax credit of €1,650 per year. The credit is also available to those receiving taxable social welfare payments.
Medical expenses
All qualifying medical expenses can be claimed as a tax credit at a rate of 20%. For example, if you spent €200 in a year on medical expenses, you receive a tax credit of €40.
For dental expenses, they must be non-routine treatments which are listed here.
To claim your medical expenses, you can make the claim on-line through PAYE Anytime or by submitting a Form Med 1 or Form Med 2 (i.e. for dental expenses) to your local Revenue office.
Rent tax credit
Strictly speaking, this credit is no longer available to those seeking to claim it for the first time. However, if you were renting a residential property on or before 7 December 2010, you will be able to claim the credit which currently amounts to €160 per year provided that the rent paid in the year was over €800.
Single person child carer credit
This credit of €1,650 is available to a single parent with a qualifying child living with them.
Home carer's credit
A credit of €810 is available to a married person who principally stays at home to mind a dependant (i.e. a child or older person). The claimant cannot have income in excess of €5,080 in the year and the joint income of the married couple cannot exceed €41,800.
The above are the main credits availed of, however, there are many others including Start Your Own Business Relief, Tuition Fees, Blind persons credit, Age credit credit etc. Most of these can be claimed on PAYE Anytime but also by calling your local Revenue Office.
So, you should check your tax credit certificate to ensure that you are receiving all the credits available to you. If you have any questions on any of these, let me know in the comments below.