It is Permissible to delay making up missed Ramadan Fasts until before the next Ramadan comes, and this is for those who broke the fast for a reason such as sickness, travel, menstruation and the like

Sahih Muslim · Book 13 · Hadith 1146 c

وَحَدَّثَنِيهِ مُحَمَّدُ بْنُ رَافِعٍ، حَدَّثَنَا عَبْدُ الرَّزَّاقِ، أَخْبَرَنَا ابْنُ جُرَيْجٍ، حَدَّثَنِي يَحْيَى، بْنُ سَعِيدٍ بِهَذَا الإِسْنَادِ وَقَالَ فَظَنَنْتُ أَنَّ ذَلِكَ لِمَكَانِهَا مِنَ النَّبِيِّ صلى الله عليه وسلم ‏.‏ يَحْيَى يَقُولُهُ ‏.‏

In another version of the previous hadith, the words are:" Yahya said: I think it was due to the regard for the Messenger of Allah (ﷺ)."

Sahih Muslim · Book 13 · Hadith 1146 d

وَحَدَّثَنَا مُحَمَّدُ بْنُ الْمُثَنَّى، حَدَّثَنَا عَبْدُ الْوَهَّابِ، ح وَحَدَّثَنَا عَمْرٌو النَّاقِدُ، حَدَّثَنَا سُفْيَانُ، كِلاَهُمَا عَنْ يَحْيَى، بِهَذَا الإِسْنَادِ وَلَمْ يَذْكُرَا فِي الْحَدِيثِ الشُّغْلُ بِرَسُولِ اللَّهِ صلى الله عليه وسلم ‏.‏

This hadith is reported on the authority of Yahya with the same chain of transmitters but no mention is made of the duty to the Messenger of Allah (ﷺ).

Sahih Muslim · Book 13 · Hadith 1146 e

وَحَدَّثَنِي مُحَمَّدُ بْنُ أَبِي عُمَرَ الْمَكِّيُّ، حَدَّثَنَا عَبْدُ الْعَزِيزِ بْنُ مُحَمَّدٍ الدَّرَاوَرْدِيُّ، عَنْ يَزِيدَ بْنِ عَبْدِ اللَّهِ بْنِ الْهَادِ، عَنْ مُحَمَّدِ بْنِ إِبْرَاهِيمَ، عَنْ أَبِي سَلَمَةَ بْنِ عَبْدِ الرَّحْمَنِ، عَنْ عَائِشَةَ، - رضى الله عنها - أَنَّهَا قَالَتْ إِنْ كَانَتْ إِحْدَانَا لَتُفْطِرُ فِي زَمَانِ رَسُولِ اللَّهِ صل…

'A'isha reported: If one amongst us had to break fasts (of Ramadan due to natural reasons, i. e. menses) during the life of the Messenger of Allah (ﷺ) she could not find it possible to complete them so long she had been…