Form 49b is one of the application forms mentioned in the Income Tax Act 1961 under section 203A. This application form is responsible for assigning TAN, i.e., the Tax Deduction Account Number. Tax Deduction Account Number is a unique number of 10 digits assigned to all those responsible for collecting the tax in place of the Income Tax Department. The Tax Account Deduction Number registration is necessary for the deduction of the Tax Deducted at Source on transactions.Â