All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
As regards the issue of the arrival of the husband on the 30th day of Ramadan and having intercourse with his wife, then our answer is as follows:
1- The husband in not obliged to fast that day, because he was travelling during the day and thus was not obligate to fast. Therefore, he is not obliged to fast after arrival according to the preponderant opinion of the scholars like Imaam Maalik and others .
2- If a traveller comes back from his travel while he is not fasting and then he has intercourse with his wife, he is not obliged to expiate for that; this view is reported by Imaam Ahmad but he is sinful for invalidating the fasting of his wife, and he is obliged to repent to Allaah.
3- If the wife is forced to have intercourse, then she is not obliged to expiate for it. Ibn Qudaamah said: ''If a wife is forced to have intercourse, she is not obliged to expiate for it; there is only one narration in this regard (without any difference of opinion) but she has to make up for this day." However, if she incited her husband, then she is greatly sinful and she is obliged to sincerely repent to Allaah fulfilling all the conditions of a sincere repentance. Whoever sincerely repents, Allaah will accept his repentance. However, there is a difference of opinion among the scholars whether or not she is obliged to expiate, some of them are of the view that she should expiate for that whereas some others are not of this view but to be on the safe side, a woman should expiate.
For more benefit on the definition of expiation, please refer to Fatwa 84189, and for the conditions of a sincere repentance, please refer to Fatwa 87903.
Allaah Knows best.