Unlike Arab cultures, the Niyat is not repeated at Iftar. Instead, a specific Dua (prayer) is recited: "Allahumma laka sumtu..."
The concept of Niyat is rooted in the Prophetic tradition which states that actions are judged by their intentions. For the fast (Nombu) to be valid, the believer must make a conscious mental or verbal commitment before the fast begins. This typically happens between the time of Iftar the night before and the start of Fajr (dawn). While the Niyat is essentially an act of the heart, many choose to recite specific Arabic phrases or their translations to solidify their commitment and focus. nombu niyat
In strict Arabic, Niyyah is silent in the heart. However, Tamil Muslim scholars (Muftis of Kayalpattinam and Nagore) argue that verbal utterance helps eliminate doubt and reinforces sincerity for non-Arabic speakers. Unlike Arab cultures, the Niyat is not repeated at Iftar
If you forget to verbalize the niyat but had the mental intention to wake up for Suhoor (pre-dawn meal) for the purpose of fasting, your fast is generally considered valid. This typically happens between the time of Iftar