Visitor Visa documents required for self employed

[shray]

I have a question regarding Visitor Visa documents required for self employed. I am planning to process visitors visa for my in-laws. My father-in-law is a Self employed and mother-in-law is a house wife. My question now is what documents are required to prove monthly income and proof of business for self employed people.

It would be of great help if some one can give me details.

Thanks in advance

[kabkaba]

Your documents will only be needed in case you are paying for their trip.
In any case tax returns are generally the best way to show the income. Also having bank statements showing ability to pay for the trip are also needed.