When should I make intention for Ramadan fasting?

How can I keep fast when I can't get up for sahur? When should I make my niyyah?

If a person cannot get up for sahur, he should make his niyyah (intention) for fasting before the noon

According to the Shafi madhab, if it is an obligatory fast, the intention should be made at night, it should not be delayed for the morning. Otherwise, it should be compensated after the eid.

However, according to the Hanafis, the intention can be made both at night and in the morning (till the noon) for the Ramadan, nafila (optional)and vow fastings.

With respect to this point Ibn-I Hajar says that when a Shafi Muslim forgets to make niyyah at night for Ramadan fasting, he shall follow (imitate) the Hanafi madhab for this case and make his niyyah before the noon. This permission is because of the importance of the Ramadan fasting. Our Beloved Prophet (pbuh) states that “If anyone omits his fast even for one day in Ramadan without a concession or without being ill, then if he were to fast for the rest of his life he could not make up for it.” (Bukhari)

According to the Maliki school of thought, it is enough to make a niyyah at the beginning of the month of Ramadan. It is not necessary to repeat the intention every night.

So, for the Shafi and Hanafi Muslims,  it’s better to make their niyyah at the beginning of the Ramadan; because, if they forget to make intention for one day, their fast will be valid according to the Maliki madhab. (The Encyclopedia of Islamic Fiqh) thus, they will not be deprived of the Ramadan fasting just because of forgetting or being late for the intention.

As a consequence, the fast of a person who is late for sahur will be valid as long as he does not eat anything and make intention before the noon.