UnitedHealth Group Inc. has extended the deadline to complete its proposed $7.8 billion acquisition of Change Healthcare Inc., according to a filing from Change Wednesday.

UnitedHealth told Change on Dec. 9 “that it was exercising its unilateral right to extend” the outside date for the merger to April 5, the filing said. The companies’ merger agreement gives both sides the right to push back the deadline.

A UnitedHealth spokesman referred to recent remarks in which executives said the company is working to satisfy requests from regulators and that it expects to complete the deal in the first part of …