RTI is applicable only to Govt. Organizations. Private school need not give salary details. But IT department being Govt. Organization has to give the information under RTI. So file RTI showing HC judgement. If you want to get salary details, the proper course of action is to file application before the court summoning salary record from the employer, where he is working. If you want his Income Tax return, then you can move proper application before the court seeking the direction to the spouse to produce the IT return, but for that you have to satisfy the court, why IT return is important.