Intending at night to observe Sawm on the next day
If it is a Wajib (obligatory) Sawm, such as Sawm of a vow or making up for a missed day in Ramadan, it is impermissible to break Sawm. Breaking an obligatory Sawm without an excuse is a sin, and (Part No. 9; Page No. 151) they must make up for that day. However,
if it is a supererogatory Sawm, it is better to complete Sawm. If Sawm is broken, there is nothing wrong in this and making up for it is not required.May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.