The Halachic principle of Tashlumin allows a person to make up a missed prayer at the time when he recites the subsequent prayer. For example, if a person forgot to recite the Minha prayer, he makes up the missed Tefila by reciting an extra Amida prayer at Arbit. The first Amida prayer is recited as the regular Arbit prayer, and the second Amida makes up for the missed Minha prayer.
An interesting question arises in the case of a person who remembered that he forgot a prayer well after his recitation of the subsequent prayer. Consider, for example, the case of a person who returned home from Arbit, ate dinner, did some work, and later, at 11pm, suddenly realized that he had forgotten to recite Minha that day. On the one hand, one might argue that the Tashlumin prayer must be recited in conjunction with the subsequent prayer, and thus once this person finished Arbit and moved on to other activities, he lost the opportunity to make up the missed Minha. On the other hand, we might claim that since the time for Arbit has not yet passed, he can still make up the missed Minha prayer.
The Shulhan Aruch (Orah Haim 108:3), in the context of the laws of Tashlumin, writes, "This [concept], that one can make up a prayer that he had missed, applies only during the time of the adjacent prayer, but not at a time that is not the time for that prayer." It appears from this formulation that the Shulhan Aruch allows reciting the Tashlumin prayer at any point during the period in which the subsequent prayer may be recited. Even well after one had recited the subsequent prayer, he may still make up the missed prayer, so long as the time-frame for the subsequent prayer has not yet passed. In the aforementioned case, then, it would seem that according to the Shulhan Aruch, the individual may still recite the Amida to make up the missed Minha prayer, since the latest time for Arbit had not yet passed.
This is, indeed, the ruling of Hacham Ovadia Yosef. He adds, however, that since some authorities dispute this ruling, a person in this case should preferably recite the Amida on condition. Meaning, he should stipulate before reciting the prayer that according to the view allowing him to make up the missed prayer at that point, it should count as the Tashlumin prayer, but according to the other views, it should be counted as a voluntary prayer. This way, one satisfies all views among the Halachic authorities.
A similar question arises in the case of a person who forgot to recite Arbit, but does not realize his mistake until late the next morning, well after he recited Shaharit. Halacha designates two different "deadlines," so-to-speak, for the recitation of Shaharit. In order to fulfill the Misva of praying at the proper time, one must recite Shaharit within the first four hours (as defined by Halacha) of the day. If one did not pray Shaharit within that time-frame, he should still pray, as long as it is still before Hasot (midday as defined by Halacha), in which case he receives credit for praying, but not for praying at the proper time. (Incidentally, Hacham Ovadia Yosef rules that ten men who had not recited Shaharit before the end of the fourth hour may pray Shaharit together a Minyan, with the repetition of the Amida, until Hasot.) The question thus arises as to whether one can recite a Tashlumin prayer to make up a missed Arbit in between the fourth hour and Hasot. Does the opportunity for Tashlumin end once the preferred time for Shaharit passes, or does one still have the opportunity to make up a missed Arbit until Hasot the next day?
Hacham Ovadia rules that in this case, too, one should recite the Tashlumin prayer, but stipulate that according to the view that he cannot recite Tashlumin at this point, the prayer should count as a voluntary prayer. Since the final time for Shaharit has not yet passed, he can still make up a missed Arbit prayer, but he should nevertheless make this stipulation in order to satisfy all opinions.
It must be emphasized that once the final time for the current prayer has passed, one may no longer make up the previous prayer. Thus, for example, if one remembers after sundown that he had forgotten to recite Shaharit, he cannot recite a Tashlumin prayer to make for the missed Shaharit.
Summary: A person who accidentally missed a prayer should recite an extra Amida after reciting the Amida of the next prayer. For example, one who forgot to recite Minha recites an extra Amida after the Amida for Arbit. If he does not remember his mistake until well after his recitation of the next prayer, then he may still make up the missed prayer by reciting the Amida, provided that the final time for the current prayer has not yet passed. In such a case, however, one should preferably stipulate that according to the view that it is too late to make up the missed prayer, the prayer should be considered voluntary. This Halacha also applies to one who forgot to recite Arbit and remembered his mistake in between the fourth hour of the next day and Hasot (midday as defined by Halacha).

Daily Halacha
Until What Point Can a Person Make Up a Missed Tefila?
Lectured by Rabbi Eli Mansour
