Six months ago, Republicans in Congress joined with President Trump to redesign America’s tax code and enact sweeping tax cuts. We were determined to let families and local businesses keep more of what they earn. The new tax code was built to help American companies and workers compete and win anywhere in the world.

Now something big is happening to America’s economy. Since January, more than one million jobs have been created. This has brought claims for unemployment benefits to their lowest level since 1969, and there are...