In muslims generally registration of marriage does not holds a great importance. But still due to legal rules it may be done. Muslim men can marry a girl of any community except jewish and christian. The children born out of such marriage follow islam. If a muslim girl wants to marry a man of different religion then the man has to convert to islam for marriage.
For women marriage certificate holds lot of importance in case of marriage
disputes as it is a valid proof of the marriage. A marriage certificate confirms
that the children in a marriage are born out of legal wedlock. It is very easy
to apply for marriage certificate https://moodle.umn.edu/blog/index.php?postid=11414