NOTHING about the narrow cream-colored lobby at 160 Aldersgate Street in the City of London financial district gives a hint of its role at the center of the offshore oil industry.

    That’s because the building is occupied by a law firm. Yet, on paper at least, it is also home to Rowan Companies, one of the largest operators of drilling rigs in the world.

    In 2012, Rowan, which has a market value of US$4 billion, shifted its legal and tax base from the United States to Britain. But not much else.

    “We changed our corporate structure and we’re legally domiciled in the United Kingdom but our headquarters and our management team remain in the United States,” Suzanne Spera, Rowan’s investor relations director said.

    “It has been positive. We take advantage of trying to be competitive with our effective tax rate.”

    Indeed, Rowan filings say the shift helped cut the company’s effective tax rate to 3.3 percent in 2013 from 34.6 percent in 2008. Spera said Rowan complies with all U.K. tax rules.

    A government spokeswoman for the Treasury said recent changes to the tax rules were aimed at supporting “genuine business investment.”

    “The United Kingdom is not a tax haven. In 2015, our main rate of corporation tax will be 20 percent, well above the levels seen in tax havens,” she said in an emailed statement.

    In the past year around a dozen major U.S. companies including media group Liberty Global, banana group Chiquita and drug maker Pfizer unveiled plans to shift their tax bases overseas outside the United States.

    Historically, when U.S. companies wanted to cut their tax bill they usually reincorporated in Caribbean Islands or Switzerland.

    However, following recent legal changes whereby Britain largely stopped seeking to tax corporate profits reported in other countries, including tax havens, companies are increasingly choosing the United Kingdom as a corporate base.

    There is no official list of companies which have moved their tax base to Britain but government officials, tax advisors and lawyers said at least seven had re-based to London.

    (SD-Agencies)