We had nikah with my girlfriend without informing our families one year ago. There is no engagement or civil marriage. Our families still do not know and we separated. Now I heard that nikah without the girl's supervisor's permission was invalid. I had promised to pay 20 golden coins as mehr. Do I still have to give her that mehr?
If marriage (nikah) was performed without the information and permission of the bride’s family, then that marriage is invalid. However, you have to pay the mehr if the marriage was consummated. If not consummated, you do not need to pay the mehr.
Below is a relevant hadith:
أَيُّمَا امْرَأَةٍ نُكِحَتْ بِغَيْرِ إِذْنِ وَلِيِّهَا فَنِكَاحُهَا بَاطِلٌ فَنِكَاحُهَا بَاطِلٌ فَنِكَاحُهَا بَاطِلٌ فَإِنْ دَخَلَ بِهَا فَلَهَا الْمَهْرُ بِمَا اسْتَحَلَّ مِنْ فَرْجِهَا فَإِنِ اشْتَجَرُوا فَالسُّلْطَانُ وَلِيُّ مَنْ لاَ وَلِيَّ لَهُ ”