Married - but never changed tax stautus

jj o sull

Registered User
Got married a few years ago - but neither my wife or I ever changed our tax status.
She is a public sector PAYE worker - salary approx 60K.
I am private sector PAYE worker - salary approx 85K.

No other outside income - or claims to revenue for any relief on anything during this time.

Would it more beneficial for both of our weekly take home pays to be joint assessed - if we changed our status online now without doing anything like moving credits around ?
Can we apply to back date this change and see if any tax back would be due?
Would it be possible that we could accrue a tax bill in an assessment like this?

Thank you.