This is a very planning point for married couples.
I have seen cases where the Husband has all the income, so the 20% tax band is the €44,300 for a married person with one income.
If, for example, he has a rental property, he should convey it to her, as she can earn up to €26,300 at 20%.
Or sometimes they stuffed the husband's pension fund when they would be better off contributing to her pension fund so that she will have her own income in retirement. This would only apply if she were getting tax relief at 40% on her contributions, which I presume she would be getting.
Brendan