U.S. fast-food chain Burger King Worldwide Inc. and Canadian coffee-and-doughnut chain Tim Hortons Inc. have agreed to an $11.4 billion tie-up that would send the combined company’s headquarters north in what may be the most visible corporate tax inversion yet.

Inversions have been growing in popularity as more U.S. companies seek to avoid high corporate taxes at home by acquiring companies in those foreign countries where the tax rates are lower. But the strategy has met with fierce opposition by lawmakers as well as the Obama administration.