Some countries make tenders mandatory. In the United Kingdom, for instance, a buyer who obtains at least 30 percent ownership with a tender has to accept offers from other shareholders to sell at the same price. In the United States, tenders are non-mandatory. If the buyer wants 51 percent ownership and gets it, he doesn't have to offer the other 49 percent anything.
Stock reorganizations take place when two companies merge or one buys up the other. The reorganization often involves swapping stock in the old companies for the new merged corporation, but it may also include a tender. If it's non-mandatory, the company doesn't have to make the offer to all stockholders. If the offer is for less than 5 percent of the stock, it's also free from many of the federal disclosure rules applying to larger tenders.