In India, a tax audit is a process of examining and verifying the books of accounts and other financial records of a taxpayer to ensure that the income, deductions, and other financial transactions reported by the taxpayer are accurate and comply with the tax laws of the country. Tax audits are conducted by the Income Tax Department of India, which is responsible for administering and enforcing the tax laws of the country.

The tax audit is mandatory for certain categories of taxpayers, such as companies, firms, and individuals who meet specific turnover and income criteria. The tax audit is conducted by a Chartered Accountant (CA) who is appointed by the taxpayer and is required to submit a report to the Income Tax Department. The report includes information on the taxpayer's compliance with the tax laws and identifies any discrepancies or issues that need to be addressed.

During the tax audit, the CA may ask for documentation, information, and explanations from the taxpayer to clarify any issues or discrepancies found in the financial records. The CA may also visit the taxpayer's premises to inspect the books of accounts and other relevant documents. The tax audit typically covers a range of areas, including income, deductions, expenses, investments, and compliance with tax laws and regulations.

If the tax audit identifies any discrepancies or issues, the taxpayer may be required to pay additional taxes, penalties, or interest, as well as take corrective measures to address the issues identified. 

the threshold limits for tax audit in India ) are as follows:

1. Businesses: If a business has a turnover of more than INR 1 crore in the financial year, then it is required to undergo a tax audit.
2. Professionals: If a professional, such as a doctor, lawyer, architect, etc., has gross receipts of more than INR 50 lakh in the financial year, then he/she is required to undergo a tax audit.