Ok, basically when married assuming you opt for joint assessment, which in my experience is the most common basis of assessment selected by married persons, ( I'm not going to go through the other bases of assessment, they are on the Revenue site and can be read there ), you can combine your tax credits and cut-off point so that in certain circumstances you may be better off tax wise than staying assessed as single individuals. The extent to which you will benefit depends on your earnings as between you and your spouse.