Dublin, Ireland. Photo credit: Shahid Khan/Shutterstock.com

In the past week, there’s been discussion of how the U.S. Senate’s tax bill could affect every sector of the country’s economy. But the tech industry needs to think about more than just the bill’s national repercussions.

Tech’s biggest companies—including Twitter, Google and Apple—are all multinational, with European headquarters in Ireland. The country has long lured American tech companies with its low corporate tax rate of 12.5 percent and several have been accused of using Irish subsidiaries to avoid large non-U.S. revenue taxes. Now, there are thousands of American tech employees in Ireland, working in offices along Dublin’s Silicon Docks.

But the latest tax bill could jeopardize tech companies’ expansion into Ireland and other international markets. It passed the Senate in the early hours of Dec. 2, but will still have to pass the House to become effective through a vote that hasn’t yet been scheduled. The House’s version of the bill, still in development, may differ somewhat.

“The Senate bill makes the U.S. much more favorable as a jurisdiction to earn profits in,” said John Ryan, a Silicon Valley-based partner at Morgan, Lewis & Bockius, who has worked in both Ireland and the United States. “It also makes it easy so that if you have moved IP offshore, you get three years to bring it back to the U.S. tax free. It encourages that.”

The bill would lower the corporate tax rate in the United States from 35 to 20 percent. And this lower rate, potentially drawing multinational tech firms back home, isn’t happening in a vacuum.

There have been increased efforts from the Organisation for Economic Co-operation and Development and the European Commission to ensure major corporations are not avoiding paying tax to the countries where they operate by holding small offices elsewhere, Ryan says.

And while this wouldn’t necessarily impact major companies with international homes away from home in Ireland, as most of their offices include employees doing real work, tech firms of middle size that haven’t built their overseas offices extensively may be inclined shutter these outposts. If having offices offshore means spending more time and money building those offices, a lower tax rate in the United States may be enough to bring them home and keep them there.

“If the [final tax] bill that passes looks something like the form of the Senate bill, then there will be a much greater likelihood that they say ‘let’s collapse’ [overseas], we have enough substance at home,’” Ryan said. He said it could also keep domestic companies from opening their first international bases, and that there’s already been concern expressed in Ireland.

But Mark O’Sullivan, an Irish tax lawyer and a partner at Matheson based in Palo Alto, says it is important to note that, at least in Ireland’s case, low tax rates aren’t the only attraction for tech companies. Companies based in Dublin, Cork and other parts of the Emerald Isle have access to the European Union via an English speaking country—and soon, post-Brexit, the only EU English-speaking country. It’s a benefit that could outweigh the tax implications for U.S. tech firms.

“Companies are in Ireland for access to the EU market,” O’Sullivan said. “Brexit is highlighting how important that is.”

It’s a perk general counsel and other tech company leaders will likely keep in mind going forward as they formulate plans to respond to potential tax reform and weigh the potential gains against the downsides.

“I think 2018 will be a year of a lot of planning,” Ryan said. “There will be a lot of thinking through pros and cons.”