<s>[INST] Why is it necessary to have TAN? [/INST] ​​​​​​​​​​As per section 2​03A of the Income-tax Act, 1961, every person who deducts or collects tax at source has to apply for the allotment of TAN. Section 203A also makes it mandatory to quote TAN in TDS/TCS return (including any e-TDS/TCS return), any TDS/TCS payment challan, TDS/TCS certificates and other documents as may be prescribed. As per section 272BB, failure to apply for TAN or not quoting the TAN in the specified documents attracts a penalty of Rs. 10,000/-. </s>