Getting Hitched

If you each earn above the 42k SRCOP, marriage makes no difference to income tax.

Of course, there are other benefits to marriage.

Put it another way, there is no disadvantage to joint assessment.

If for example, a spouse went on maternity leave and lower income, there could be unused lower rate bands to transfer

The only time separate assessment makes any sense is if both parties are self employed earning well over the standard rate cut off and prefer to keep tax payments separate for their own finances, but even then down the line there will likely come a few years where joint assessment will be preferred

Bad advice. Joint assessment has to be requested by 31 March to apply for the year in question. I've seen plenty of tax overpaid because people didn't just make that one simple change. Which doesn't affect them either way at the time.

A lot of people think joint assessment can be back dated 4 years, like claiming tax relief on medical expenses. It absolutely can't.

And if a couple's circumstances change after 1 April, and one of their incomes falls below the standard tax band threshold, they will needlessly overpay income tax in that year which could so easily be avoided by simply being jointly assessed.

And if they ask Revenue to backdate their joint assessment they'll be firmly told no.