General Brazilian
prorrogar o prazo / estender o prazo
Most commonly used in business and formal contexts
Rio de Janeiro
prorrogar o prazo
Standard usage in professional settings
São Paulo
estender o prazo / prorrogar o prazo
Both terms widely accepted in business environments
Portugal
prorrogar o prazo / alargar o prazo
Both terms used; 'alargar' is also common in Portuguese European