convenience marriage
sham marriage
https://en.wikipedia.org/wiki/Category:Sham_marriage
https://en.wikipedia.org/wiki/Sham_marriage
A marriage of convenience entered into without intending to create a real marital relationship. This is usually for the purpose of gaining an advantage from the marriage.
Definitions of sham marriage vary by jurisdiction, but are often related to immigration. The essential point in the varying definitions is whether the couple intend to live in a real marital relationship, to establish a life together.
fake marriage
sham marriages