Dear Sarika,
You can request for the candidates last 6 months salary slip
or Check with the HR of that company (this can be initiated once the candidate has accepted the offer. )
Or the last option is - to check the bank statements of the candidate in the last few months.
Apart from the above - prepare a salary standard based on what is the norm in your industry, and remember to segreggate them as tier 1, tier 2, tier 3 companies. Reason: You cant hire a person in your industry, who comes from a tier I (ex: MNC), and expect him to join at a lower salary. Same way - you cant take a person from a tier 3 company and give him a direct 100% hike. Also - education matters. So keep all this as a part of your criteria.
Map where your company stands (is it Tier 1? tier 2? or tier 3?") this can be based on the turnover / location, etc - the criteria for this has to be discussed and finalized by the top management too.
Hope this helps.