Imagine you own a successful U.S. company and you transfer its most valuable assets—a factory, a patent, or even the whole business—to a foreign corporation. Under normal corporate tax rules, you might expect that transfer to be tax‑free, just like a domestic incorporation. But Congress sends a clear message: if you move appreciated property out of the U.S. tax net, you generally must pay tax on the built‑in gain. This chapter explains the special toll‑charge rules that apply when U.S. persons transfer property to a foreign corporation in what would otherwise be a tax‑free reorganization.