Can a sponsored worker work overseas during a visa extension?
A sponsored worker whose Skilled Worker visa is being extended must generally remain in the UK while their application is pending. Section 3C leave, which continues their right to work while a valid in-time application is under consideration, ends at the point they leave the UK.
Short trips may be possible in some circumstances but you should contact Borderless before any overseas travel is booked during a pending application. Incorrect travel can void the application.
The 28-day delayed start rule
When a CoS is assigned, the worker's employment must generally start within 28 days of the later of the CoS start date, the visa grant date, or the worker's arrival in the UK. If the worker does not start work within 28 days, the sponsor must report this as a change of circumstance and may need to withdraw the CoS.
A delayed start of more than 28 days for a genuine, documented reason (for example a serious medical issue or flight disruption) can sometimes be accepted, but you should notify Borderless and the Home Office at the earliest opportunity.
Working remotely from overseas
Sponsored workers cannot routinely carry out their sponsored duties from outside the UK. Occasional short overseas work trips as part of their UK-based role are usually acceptable. Extended overseas working is not compatible with Skilled Worker sponsorship and may require a change to the worker's immigration status.
Government guidance: https://www.gov.uk/guidance/sponsor-a-skilled-worker#worker-circumstances
Delayed starts in the UK: which dates count, what to report, and pay
The 28 days run from the latest of the following: the start date on the CoS (taking into account any changes you reported before the application was decided), the "valid from" date on the worker's entry clearance vignette, or the date the worker is notified that entry clearance or permission to stay has been granted. Since most workers now receive an eVisa rather than a vignette, the notification date is often the relevant one. Note that under current Home Office guidance the worker's arrival date in the UK is not one of these trigger dates.
A worker cannot start before the visa "valid from" date, but starting later than the CoS start date is fine, provided they start within the 28-day window. No report is needed for a delayed start within the window.
If the worker will not start within 28 days, you have two options. If you wish to continue sponsoring them, report the new start date and the reasons for the delay via the Sponsor Management System. Otherwise, report that they have not started. Either report must be made by the end of 10 working days after the 28-day period, using the "Report migrant activity" function.
On pay: your salary obligations begin when the worker actually starts work. You are not required to pay a worker from the CoS start date if they have not yet started. Once they start, they must be paid in line with the salary and hours on their CoS, and your records (payslips and start date reports) must be consistent with the actual start date.
Government guidance: Workers and Temporary Workers: guidance for sponsors part 2