Brazilian financial-technology company Nu Holdings Ltd. is considering plans to shift its legal base to the UK, in a move that would mark a major win in Britain's push to encourage more tech companies to move to the country.

The digital challenger bank has been working with the British government on the plans, which were discussed as part of a broader set of agreements between Brazil and the UK on Tuesday on the sidelines of the Group of 20 leaders' summit in Rio de Janeiro, according to people familiar with the talks.

The change in domicile was not included...