American companies in Belgium want the next federal government to further lower the country’s corporate income tax rate to below 20 percent.

Following a major corporate tax reform agreed to by Belgium’s center-right government in 2017, the tax rate is set to drop to 25 percent in 2020. But U.S. companies with subsidiaries and affiliates in Belgium want the next government to go even further after the May 2019 general elections.

“To be more competitive with neighboring countries, we need a reduction below 20 percent” of the corporate rate, An De Reymaeker, a partner at the Vandendijk & Partners law...