By imposing a tax the company must raise the price of the goods to pay for the tax (or produce the good more cheaply, say with fewer inputs, which reduces the quality of the good somehow, which is the same as raising the price). At a higher cost, fewer goods are sold and so the firm has less revenue and thus lower total profits as well as hiring fewer workers. So the tax burden falls on workers, consumers, shareholders. Exactly how it falls on each group is the theory of tax incidence which has nothing to do with whomever needs to collect the tax for the government. The fact that A collects the tax and sends the check does not mean that A pays the tax.