Hello Nishtha,
From the link, Asivad shared, it clearly states that:
"if the applicant is self-employed, articles of incorporation or other evidence of business ownership, evidence of self-employment income, and documentation from third-party individuals indicating the service provided along with payment details (self-declared main duties or affidavits are not acceptable proof of self-employed work experience)."
Regarding Income Tax, i think it would be wise to include it. For Self employed, you need to provide everything that supports your case.