(for people or transactions that cross a US Border)
Special tax returns are generally required for people who move to the US, and for transactions that cross a US border. A number of these tax forms entail subtle nuances, so if they are not filed or if they are filed but completed incorrectly, the consequences can be costly (see Tax Return Question?).
For example, non-US ownership of US corporations needs to be specifically reported under certain circumstances. Where US persons own interests in, or are directors of, a foreign company, this also requires specific reporting (see Non-US Entity?).
Specific reporting is also required where a US person makes a transfer to, or receives a distribution from, a foreign trust (see Foreign Trust?).
Where a person moves or immigrates to the US, special tax reporting is generally required for the year that they transition to US tax residency (see Moving to the US?).