Remote working in the US for up to 6 months - tax implications?

Hi, I am working at a UK unversity and am undertaking a period of 'scholarly activities' (research) at a US university for up to 6 months. At the same time I will be undertaking some of my regular UK duties, remotely. Thus, my 6 months will be approximately 50% scholarly activities, 50% university duties. My employer has raised the issue of 'tax implications' related to remote working in the US. What these implications are, however, unclear. I can confirm that I will not be in the US for the period required to pay social security, and my visa (O3) permits scholarly activities so long as there is no US-based salary/payment. (I am required to show I have UK salary during my time in the US.) Is there any requirement for my employer to set up a payroll in the US? Are there any other considerations on their part that is relevant to HMRC? Thank you for any information on this.

Hi
Your employer can contact HMRC and seek a direction to operate PAYE on an employees earnings, by filling out and submitting the form at (Apply for a direction to operate PAYE on an employee's earnings) your UK earnings, while you are resident in the USA.  They will continue to deduct class 1 national insurance from your earnings, during this period.  You will also need to complete a self assessment tax return after the tax year has ended.  Your employer does not need to set up a payroll in the USA, as the S690 direction will be sufficient.

Thank you, this is extremely helpful. Just to make sure I am taking the right information back to my employer, would this be an accurate summary? (There is some confusion at their end as to what is relevant in both the UK and the US in terms of remote working.) - I am temporarily residing in the US for not more than 6 months and am not being paid by a US employer, as such I will remain under the UK National Insurance system (and will not need to pay into the US Social Security system). However, I may need a Certificate of Coverage from HMRC to demonstrate that I am covered under the UK social security system. - The S690 direction will allow my employer to continue operating PAYE as if I was still physically working in the UK, even though I am temporarily abroad. This will ensure that my tax and National Insurance obligations remain with the UK, and that I won't have to worry about tax withholding requirements in the US. Many thanks.

Hi eferedoes,
Under S690 rules, your employer will be able to deducted tax on that part of your income that is carried out in the UK and pay the remaining income tax free, so that you can declare it in the USA.  They will continue to deduct class 1 NIC on your entire income, as the UK/USA tax treaty does not include national insurance payments.  You will receive a P60 after the end of the tax year.  This will show your national insurance payments for the tax year as well.
Thank you.