Suppose Kiddush were forgotten on Leil Shabbat. Would a person be allowed or even required to do Tashlumin and then recite Kiddush during the daytime since it was missed the previous night?
Based on a statement from Pesachim 105a, if Kiddush was not said on Friday night either by accident or on purpose it can be said the entire next day (Rambam Shabbat 29:4, Shulchan Aruch OC 271:8), with the exception of the introductory paragraph of Vaychulu which is only said at night as that is when the creative work was originally finished (Rama, ad loc).
Although Amram Gaon (quoted in the Tur OC 271) held that Kiddush may only be made up during the day if it was forgotten at night by accident just like regular Tashlumin, this position is not accepted lehalacha. The disagreement can be based on how each understands the nature of kiddush: if kiddush is actually sanctifying the day, then it would have to be said at night and saying it during the day would only be a make-up; however, if kiddush is our declaration that the day is naturally sanctified, then saying it during the day would be the same as saying it at night only later. It would seem then that we hold like the second view.
+1. Re "The disagreement can be based...", is this your conjecture, or do you have a source for it?– msh210 ♦May 16, 2012 at 14:36
@msh210 Lemai Nafka Minah? This is lomdus not halacha. IAE I heard the explanation from a friend who was learning Arvei Pesachim. I can't imagine he's the first to suggest it.– Double AA ♦May 16, 2012 at 16:34
@DoubleAA, your answer doesn't contain any mention of your having heard it from a friend. You could add that, and it might also make sense to state that you don't know his original source, unless your friend is a noted scholar.– Seth JMay 16, 2012 at 17:28
@SethJ (I happen to think very highly of this particular friend.) I'm not sure why it can't just be taken on it's own merit, as there is no Nafka Mina leHalacha. Sources back up claims that need backing. Why does this need backing? Anyone can say a svara in a machloket if it makes some sense.– Double AA ♦May 16, 2012 at 17:40
It's not that. That was a suggestion to make it sound less like it's out of the blue. It's saying "this idea speaks to me, although I must admit that I don't have a classical source for it". But the main thing is that you haven't even cited your friend. Your first mention of the friend is in your comment: "IAE I heard the explanationfrom a friend who was learning Arvei Pesachim. I can't imagine he's the first to suggest it." I happen to like your (friend's) explanation, btw.– Seth JMay 16, 2012 at 18:22