If the fasting of Ramadan is obligatory for the person, then it is forbidden for him to have intercourse during the day in Ramadan. If he breaks his fast after sunset, it is permissible for him to have intercourse.
Except for the one who is in i’tikaf in the masjid; it is not permissible for him to have intercourse even during the night of Ramadan.
(It has been made permissible for you to be intimate with your wives during the nights preceding the fast. Your spouses are a garment for you as you are for them. Allah knows that you were deceiving yourselves. So He has accepted your repentance and pardoned you. So now you may be intimate with them and seek what Allah has prescribed for you) Al-Baqara 2: 187
إذا كان صيام رمضان و هو واجب على المكلف فيحرم عليه الجماع في نهار رمضان فإن أفطر بعد غروب الشمس جاز له الجماع.و يستثنى من ذلك منن كان معتكفا في المسجد فلا يجوز له الجماع في ليل رمضان.
(أُحِلَّ لَكُمْ لَيْلَةَ الصِّيَامِ الرَّفَثُ إِلَىٰ نِسَائِكُمْ ۚ هُنَّ لِبَاسٌ لَّكُمْ وَأَنتُمْ لِبَاسٌ لَّهُنَّ ۗ عَلِمَ اللَّـهُ أَنَّكُمْ كُنتُمْ تَخْتَانُونَ أَنفُسَكُمْ فَتَابَ عَلَيْكُمْ وَعَفَا عَنكُمْ ۖ فَالْآنَ بَاشِرُوهُنَّ وَابْتَغُوا مَا كَتَبَ اللَّـهُ لَكُمْ ۚ وَلَا تُبَاشِرُوهُنَّ وَأَنتُمْ فِي الْمَسَاجِدِ ۗ تِلْكَ حُدُودُ اللَّـهِ فَلَا تَقْرَبُوهَا ۗ كَذَٰلِكَ يُبَيِّنُ اللَّـهُ آيَاتِهِ لِلنَّاسِ لَعَلَّهُمْ يَتَّقُونَ )
البقرة 2: 187