Since the ITR V pertaining to F.Y 12-13 was not sent, it would not be treated as a valid return. Still such a return is kept for records and are prima facie evidence of the income, I suppose thats the case here
If the demand is correct then its good that system adjusted it
Check why they have raised the demand of this amount, you can request for intimation[S.143(1)/rectification S.154] for the F.Y 10-11]
Return can be rectified within 4 year period , so if there is any mistake in that return then you can rectify it
Rectification can be done,online, by you u/s 154
If the demand is correct then let them adjust it and pay the differential , since the return is not valid in the 1st place.
If AO levies any penalty then they have to write something like penalty proceedings have been initiated or penalty notice are being issued , you would be receiving the SCN as to why penalty should not be levied on you, penalty order
[Lets not get into that until we know whether the demand is correct]
Since Tax was also deducted at source @ 10% of consultation Income I am presuming it to be of professional fee [S.194J] , And probably your wifes income was chargeable at higher slab rate so they are asking the differential
Explanation to S.194J
"professional services" means services rendered by a person in the course of carrying on legal, medical, engineering or architectural profession or the profession of accountancy or technical consultancy