Single Vs Married tax query

Hi,
I've been married twelve years. Even though I thought I sorted out my status with revenue, it now appears that both of us have been treated as single for tax purposes.
Will we be entitled to any back-tax when we update our records (or worse... liable for money)? Our circumstances are detailed below.
Thanks,
Dermot

Both worked full-time PAYE during this time. My wife has switched to a 4-day-week about a year ago. I took 28 weeks unpaid parental leave from Sept 2007 to May 2008.

Afaia there is only a benefit where one of you earned less than the SRCOP and the other earned more that the SRCOP.

You mihjt find this interesting here

Assuming that you both had been getting the correct tax credits etc as if you were single persons, then it is going to be virtually impossible for you to owe Revenue money.

On the other hand, Revenue may owe you money, depending on, as the above poster has, said, one of you is on a different tax band to the other.

NB - you will only be able to go back to 2005 to claim for any tax due back to you.