Your fast won’t be valid without intention
Intention (niyyah) is one of the most important conditions of fast. The fast is not valid without niyyah. This is why it is essential to know when the intention should be made.
With regard to niyyah, there are two types of fast:
To keep this type of fast, one needs to resolve for it either in the evening the day before or in the morning before the midday of a fast day. It is worth pointing out that the best niyyah is the one made in the evening before the day of fasting.
It is permitted to resolve for a fast before mid-day if a person has not done anything breaking his fast after imsak. If a person made something that breaks his fast, he is not allowed to resolve for a fast.
As this kind of fast is not restricted to certain time, the intention for it should be made in the evening. The intention made after the dawn is not valid in this case.
As far as niyyah for keeping fast in Ramadan is concerned, it can be made either in the evening or in the morning. As a rule, a person resolves for a fast after suhur (pre-dawn meal). However, if a person oversleeps suhur and does not manage to have it, he can resolve for a fast in the morning before midday on condition that after imsak he has not done anything that breaks his fast.
A person who is not going to get up for suhur in the morning can resolve for a fast in the evening. This way he does not have to get up at night to make his niyyah.
Niyyah comes from heart. Therefore, your intention is considered to be valid if you confirm it in your thought. Getting up in the morning for suhur is your intention. It is essential to make niyyah every day before the start of the next day.