Every person carrying on business comes under provisions of audit under section 44AB of Income tax Act with certain terms and conditions and threshold limits. If businesses meet the conditions mentioned in Section 44AB, their accounts must be audited by a Practicing CA (chartered accountant). 

• Main objective is to verify the correctness and completeness of the accounting records maintained by the assessee.
• Verifying the accuracy of the computations and the correctness of the income, expenses, deductions, and other relevant details provided in the tax return.
• To verify the authenticity of the documents and statements provided by the assessee, such as bank statements, invoices, vouchers and other supporting documents.
• Detecting any tax evasion or non-compliance with the provisions of the Income Tax Act.
• Other provisions of the Law. 

Audit under section 44AB is mandatory for certain categories of assessee if their annual turnover or gross receipt exceeds a specified limit. The limit for tax audit under section 44AB varies depending on the category of assessee.

• For Business: It is mandatory for all businesses whose annual turnover/ sales/ gross receipts exceeds Rs. 5 crores and also if business sales/turnover/gross receipt is less than 5 crores and excess 1 crores but business cash payment and cash receipt is more than 5 % each in business then also assessee will have to get their accounts audited under section 44AB of income tax act.
• For professionals: It is mandatory for professionals whose gross receipts exceed Rs. 50 Lakh in a financial year.
• For presumptive taxation scheme: It is mandatory for taxpayers opting for the presumptive taxation scheme under section 44AD and 44ADA, if the taxpayers is showing their profit below the limit prescribed under section 44AD and 44ADA need to get audited their books account under section 44AB of income tax act. For eligible assessees who fall under category of section 44AD the limit of sales/turnover/gross receipts refers to 2 crores. Logically with in limit of 2 crores of Turnover assessee can claim profits as per section 44AD if falls under this category.

For the assessee who falls under the category of section 44AE or section 44BB or section 44BBB threshold limit of turnover is 1 crore. Under this presumptive taxation scheme assessee can claim profit as defined in section without audit under section 44AB. If the assessee claimed his income to be lower than the profits or gains so deemed to be the profits and gains of his business in any previous year, the assessee will have to get his accounts audited under section 44AB of the income tax act.