Facebook Inc. will stop routing advertising sales of its largest U.K. clients through Ireland, increasing its tax bill by millions of pounds in a bid to improve transparency after facing criticism on tax avoidance.<br />On Monday Facebook will inform its larger U.K. customers that from April they will receive invoices from Facebook U.K. and not Facebook Ireland, a spokesman for the company told Bloomberg in an e-mailed statement.<br />The overhaul of tax structure comes after increasing global pressure on its tax affairs and as a reaction to changing tax rules, the BBC, which first reported the news said, citing unidentified sources.<br />Her Majesty's Revenue & Customs , the U.K. tax agency, said it does not comment on individual taxpayers, but said in an e-mailed statement that it "ensures that all multinationals pay the tax due under U.K. law and we do not settle for a penny less.