Our scholars have different views on this matter. Scholars of Hanafi Mazhab are of the view that it is permitted for you to make the intention for fasting the whole month of Ramadan. Scholars of Shafi’i Mazhab are of the view that it is a requirement for you to make the intention for fasting on every night of Ramadan.

Therefore, if you are concerned that you might forget to make your intention every night, you are encouraged to make the intention for fasting the whole of Ramadan at the beginning of the month. This will encompass the whole of Ramadan, including the days you have forgotten.