This is the dua which should be recited at the time of Iftar (ending the Roza / Fast).
The following Dua may be recited at the time of breaking one's fast:
ALLAAHUMMA LAKA S'UMTU WA A'LAA RIZQIKA AFT'ARTU WA A'LAYKA TAWAWKKALTU
O my Allah, for Thee, I fast, and with the food Thou gives me I break the fast, and I rely on Thee
Ameer ul-Moomineen Ali Ibne Abi Taalib (A.S.) used to recite the following du'a before Iftaar:
BISMILLAAH ALLAAHUMMA LAKA S'UMNAA WA A'LAA RIZQIKA AFT'ARNAA FA-TAQABBAL MINNAA INNAKA ANTAS SAMEE-U'L A'LEEM
In the name of Allah, O Allah, we fast, and with the food Thou gives us we break the fast, an obligation we fulfill, and Thou art Hearer, Knower
While taking the first mouthful recite:
BISMILLAAHIR RAH'MAANIR RAH'EEM YAA WAASI-A'L MAGHFIRATI IGHFIR LEE
In the name of Allah, the Beneficent, the Merciful, O He whose indulgence is boundless, forgive meRecite Soorah Al-Qadr and give alms in the name of Allah (SWT).