How to Explain Cash Salary and Validate Experience from a Sole Proprietorship to CMM Level Companies?

I am working in a sole proprietorship firm (that is not registered in MCA) in Bangalore as a software developer for almost 2 years. I am being paid in cash, so at the time of release, the firm does not provide me with a salary slip. How should I inform the interviewer about my salary?

I would like to know if the experience certificate provided by this proprietorship firm will be valid or accepted by CMM level companies.

Thank you.

For proof of salary, you may ask your employer for a salary certificate. It's a normal letter that declares your salary details. However, I doubt whether they will provide it to you or not, as they are very smart. They may not give you any letter or salary slip. In fact, they may even pay your salary in cash to avoid any controversy. But, you may try.

Thank you.