Form 26AS, What all changes there are in Form 26 AS. Form 26AS is a tax passbook containing all the details of the tax deducted from a person’s income, self-assessment tax and advance tax paid for the relevant year. Similarly, AIS is the extension of Form 26AS. It contains details of the financial transactions that are undertaken by an individual irrespective of whether the tax is deducted or not on that income. It is significant for taxpayers to cross-check the TDS certificates such as Form 16/