Tax passbook records TDS, TCS, advance and self-assessment tax payments and refunds to support taxpayer compliance. Form 26AS functions as a tax passbook documenting all major categories of tax transactions: tax deducted at source (TDS), tax collected at source (TCS), advance tax and self-assessment tax payments, and tax refunds credited to the taxpayer, thereby enabling reconciliation of tax payments and withholding credits for return filing and compliance verification.