Shulchan Arukh, Orach Chayim 67/שולחן ערוך·אורח חיים ס״ז

1The Law Regarding One Who Had A Doubt If They Recited the Recitation of the Sh'ma - Containing 1 sectionIf one had a doubt if they recited the Sh'ma, they should go back and recite it [again] and make the blessing before and after it. But if they know that they recited it, but are doubtful if they blessed before and after it, they do not go back and bless.