If you have closely watched the billing at your nearest Big Bazaar or DMART store, you will remember the cashier scanning your products with a barcode scanner. That is because each product is identified and marked by a unique barcode and product numbers. A similar identification arrangement for shares is the ISIN. Like you have codes to differentiate products in various categories, ISIN (International Securities Identification Number) is a unique 12 digit alphanumeric identification number allotted for a security (e.g. - INE383C01018). Equity fully paid up, equity-partly paid up, equity with differential voting /dividend rights issued by the same issuer will have different ISINs. This is an interesting aspect to note. If a company has issued shares and then it comes out with a bonus issue. Then the shares after the bonus will be identified with a different ISIN number, not the old ISIN number. Similarly, when rights shares are issued, the rights shares will have a different ISIN number. You must have seen price quotes for Tata Motors DVR in the newspapers. These are shares with differential voting rights (DVR). They are also identified by a separate ISIN code.
When you want to sell shares you have to issue a debit instruction slip (DIS). This is a must to sell shares. When you mention the name of the shares, you also have to mention the ISIN code in the DIS. Remember to mention the ISIN code perfectly and write all the 12 digits clearly and neatly. Ideally, you must also double check the ISIN code before issuing the DIS to your broker.