A handful of clients have asked about redomestication, which could involve buying a U.S.-headquartered company, the tax advisers said. No specific companies or deals were identified.

Uncertainties about U.S. Republican President Donald Trump's trade policies have also prompted the conversations, the advisers said.

"Inverted companies have reason to look at whether or not it still makes sense for them to be offshore, particularly those that manufacture product outside the U.S. and sell it back into the U.S.," said Pam Olson, a Washington-based tax expert at accounting and consulting group PwC.

A surge of homecomings would reverse an on-again, off-again trend since the 1980s of U.S. companies reincorporating overseas to cut tax costs.

In an inversion, a U.S. company typically buys a smaller foreign firm in a lower-tax country and adopts the acquired firm's headquarters.

That maneuver means the company does not have to pay U.S. taxes on foreign income, even if its management and operations remain in the United States.

Trump's public shaming of companies that move plants and jobs overseas has also made some consumer-focused firms rethink inversions, advisers said.

Executives at inverted companies see less tax "friction" under the new tax regime that would discourage redomiciling, advisers said, and have also mentioned the appeal of corporate-friendly, low-tax states and improved access to U.S. government contracts in the discussions.

More than 60 U.S. companies have inverted, including medical device maker Medtronic Plc. There was a wave of deals in 2011-2014, but inversions largely ended in 2015 after a regulatory crackdown by Democratic President Barack Obama.

Pfizer Inc walked away from a $160 billion merger with Ireland-based Allergan Plc in 2016 because of new U.S. Treasury rules.

The Trump administration last month finalized and left in place the Obama-era rules.

The Republican tax overhaul signed into law in December eliminated a key inversion incentive by slashing the U.S. corporate rate to 21 percent from 35 percent and altering how foreign profits are taxed.

A push to prevent profit-shifting strategies and corporate tax base erosion across the 36-nation Organisation for Economic Co-operation and Development is also making foreign tax domiciles marginally less attractive, especially in Europe.

Tax advisers said it is still possible to structure lower tax rates in countries such as Ireland and the Netherlands.

How the U.S. Treasury implements parts of the new tax law will help determine whether companies return to the United States.

A new tax on Global Intangible Low Taxed Income, or GILTI, on its face imposes a 10.5 percent tax rate. But because the bill is poorly worded, it can result in rates of 15 percent or more due to unfavorable effects on foreign tax credits.

GILTI's implementation could influence tax-base decisions among companies redomiciled in Britain, which may consider whether to relocate to the United States or other countries to avoid the effects of Brexit.

Redomiciling to the United States is a case-by-case decision, said Joe Calianno, tax partner at financial advisory firm BDO.

"It really is a modeling exercise to determine whether it's more beneficial being a U.S.-based company versus a foreign-based company," he said.

(Reporting by David Morgan; Editing by Kevin Drawbaugh and Meredith Mazzilli)

By David Morgan