It depends on how much time you cover, and how recent. In order to keep memoir being memoir, there is an essential requirement to tell the truth, to the best of our recollection. There are some things I remember word for word that happened in my childhood, but there are many blank spaces in other periods and events. (So I just say that in the narrative.) It is understood that nobody can remember every word, and that a dialogue must be built on the most sincere feelings of the event and words exchanged. That is NOT fictionalizing. That is reconstructing as honestly as possible, and the reader (and publisher) knows this without explanation. If you still feel you need to say something, you might say "Memory is always imperfect, but I have taken care to be as truthful as possible in my descriptions and dialogues of all the people I have written about here...'

Hi Nancy, great question. I am going to be starting a dialogue class soon. I will let you know if this topic comes up in my class. Congrats on starting your second memoir!