Visa could be pushed into relocating hundreds of UK jobs to other European countries following last week’s Brexit vote.
The move could be forced by an agreement in the recent £17.5bn takeover of Visa Europe by its sister company in the US.
Sky News first reported the deal included a condition that data from card transactions should not leave Europe.
Visa is understood to employ more than 1,000 people in London, with hundreds involved in data centre-related work.
No decision on job relocations is likely to be made before the terms of the UK’s future trading arrangements with the EU are close to being finalised.
A Visa spokesman said: "The process and timing for the UK leaving Europe remains unclear.
"While we continue to monitor the situation carefully, it is premature to speculate on whether possible changes to the location of our data centres would make sense or be required."