A single-member US LLC owned by a non-resident with no US-source income typically has zero US federal income tax but must file Form 5472 + a pro forma 1120.
Multi-member US LLCs file Form 1065 partnership return.
State-level franchise or annual fees still apply (e.g., Delaware franchise tax).
UK LTDs pay Corporation Tax on worldwide profits. Rates depend on profit level and start at 19%.
Always confirm tax residency rules in your own country — many countries tax foreign-controlled corporations as personal income.