Is it permissible to say: "Ya Bismillah," or should we say: "Ya Allah"?

Supplication is an act of worship, and the fundamental principle regarding adhkar (remembrances) and acts of worship is to adhere to what has been ورد (transmitted) in Islamic law. The common and correct form of supplication is "Ya Allah" (O Allah) or by using the Beautiful Names of Allah, as Allah the Almighty says: (Say, "Call upon Allah or call upon Ar-Rahman (the Most Merciful). Whichever you call upon, to Him belong the Best Names"). As for saying "Ya Bismillah" (O Bismillah), it has not been transmitted from the Prophet, peace be upon him, and it is linguistically incorrect in Arabic because "Bismillah" is a phrase whose تقدير (implied meaning) is "In the name of Allah, I begin," and it is not a name to be called upon. The predominant form for addressing the word of majesty (Allah) is "Allahumma," although the original form "Ya Allah" is also permissible.