I've just moved to the UK on a Tier 1 Exceptional Promise visa. It's good for the next 5 years, but my US passport expires in a few months. Once I've renewed my US passport, do I need to notify UKVI, and if so, what is the appropriate way of notifying them?
Yes, since the Biometric Residence Permit must be replaced when:
- your UK visa is in a passport that is lost, stolen, damaged, or expired
and the BRP is needed to prove your right to work or rent or you are travelling outside the UK.
The application can be applied for inside the above link, but only from within the UK.
In cases where the passport was lost or stolen outside the UK, a ‘replacement BRP visa’ can also be applied for in the above link which lets you re-enter the UK.
You must then apply for a replacement BRP within 1 month of your return to the UK.
According to https://www.gov.uk/transfer-visa you can use the visa in your expired passport to enter and leave the UK (you will need to carry both your expired passport with the visa, and the new passport).
You cannot use the visa in your expired passport to prove your entitlement to work. For that, you need to apply for a Biometric Residence Permit (see https://visas-immigration.service.gov.uk/product/biometric-residence-permit-replacement-service). This is yet another opportunity for you to give the UK government money. Sorry.
So, to answer your question directly: you do not need to tell the UKVI you have replaced your US passport if you just want to visit the UK; if you want to work in the UK you will need to apply for BRP (and if asked why, say that your passport has been replaced).