Hello and thank you for using Just Answer,Nonresident aliens from treaty countries who are in the United States for a short stay and also meet certain other requirements may be exempt from tax on their compensation received for personal services performed in the United States. Many tax treaties require that the nonresident alien claiming this exemption be present in the United States for a total of not more than 183 days during the tax year. Other tax treaties specify different periods of maximum presence in the United States, such as 180 days or 90 days.
Income that residents of the United Kingdom receive for services performed in the United States as employees (dependent personal services) is exempt from U.S. income tax if the residents meet the following requirements.
They are in the United States for no more than 183 days in any 12-month period beginning or ending in the tax year.
Their income is paid by, or on behalf of, an employer who is not a U.S. resident.
Their income is not borne by a permanent establishment that the employer has in the United States.
The exemption does not apply to directors' fees and similar payments received by a resident of the United Kingdom for services performed in the United States as a member of the board of directors of a company resident in the United States.If you do meet the above then you would need to file a US 1040NR and use the treaty provision of article 14. There is no limit on the exclusion and it would mean that you would recieve your income tax withholdings back as a refund.
The above is only applicable as long as you are a Nonresident Alien. If you have applied for a green card you are no longer under that status for US tax purposes and would not be covered by tax treaty either for excluding the income.