@ChikakoS , first W-9 is for taxpayers whom have SSN ( Social Security Number ), for the rest Non-Resident Alien it is W8BEN . Since you have had a valid SSN, you should use W-9 and provide your SSN.
Second, since you moved out of the country in 2021 and been here since 2018, you ( absent any other info ) were a Resident for Tax purposes and filed a form 1040 for 2020 tax year.
Third, because your permission to stay and work in the country has expired , you were employed and paid by the US entity during the period 2018 through Sep 2021 and that you would like to keep your UK earnings for the period Sep 2021 through Dec 2021 out of US taxes, you probably should file as dual status person i.e. a form 1040 covering the period Jan 1st. through the day of your departure from the USA and a form 1040-NR for the period thereafter. TurboTax does not support the prep/transmission of form 1040-NR and its schedules, you should consider using the services of a tax professional either in the USA or in the UK or SprinTax , an associate of Intuit Inc. Also note that dual status tax payers are required to use itemized deduction which can b disadvantage to be weighed against filing a Resident for the whole tax year ( and allowing taxation of the UK income by the USA ) --- but all these is best discussed with a tax professional or SprinTax or any other .
Is there more I can do for you ?
