Thank you!
So it sounds like I may not have to worry about filing in the UK, but I do know that I will have to file in the US. I can see how PAYE works and it makes sense. I guess there’s no need to file if I don’t have any other property/deductions etc since the UK government should know my salary and what taxes I’ve paid already. How do they keep track of me as a US citizen? ie, do I get assigned some equivalent of a social security number?
Is the national heath insurance paid out of my contribution to the Employee national insurance contribution?
As for the defined contribution plan, I don’t remember receiving anything about this at my job. As a US citizen will this money deducted mean anything to me? Will I ever see it?
As long as you only have sources of incomes that are reported to HMRC then you don't need to file a self assessment (SA). My sister's husband died recently and the following year she sold a second home of theirs. They each had UK share and share funds, his were sold and consolidated into her account and their financial advisor told her she need to file a SA as the combined capital gains of the share sales plus 2nd home sale exceeded her tax-free allowances. I helped her do it last year, and then just this week she filed again and yesterday received an email from HMRC telling her what she owed and that she did not need to go back to filing SA, PAYE would be sufficient.
You can run through this Q&A to see if you should be filing SA
https://www.gov.uk/self-assessment-tax-returns/who-must-send-a-tax-returnOther than reporting your income to the IRA as part of FATCA they don't keep track of you as a USC. When you get your first pay advice slip it should include your National Insurance number that has been assigned to you and is the equivalent of the US SS number. Make a note of it as it is used to track your UK equivalent of SS, which you can keep track of online.
https://www.gov.uk/log-in-register-hmrc-online-servicesYour NI insurance contributions should spelled out on your pay advice each month, and over time you can keep track of them online using the link above.
Any contributions your
employer makes to your DC plan should be reported as income when you file your US return. i.e. IRS reported income = Gross income + employer contribution to DC pension plan.