If one did not make havdala over a kos on Saturday night, whether due to circumstances beyond his control such as a soldier on a mission, forgetfulness, or even on purpose, according to the majority of Rishonim (Rambam, Tosafot, Rosh), he may make havdala until the end of Tuesday, since the first three days of the week are linked to the previous Shabbat.
Others maintain that a missed havdala can be made up on Sunday only (Ge’onim), and there is one who maintains that even this only applies if one has not eaten anything since the end of Shabbat (Behag). There are some who defer to this opinion and make havdala on a kos only until Sunday, and only on condition that nothing was eaten on Saturday night (Ben Ish Ĥai; Kaf Ha-ĥayim 299:26).
In practice, however, most poskim maintain that one who did not make havdala Saturday night, even if he has eaten, should make havdala over wine with the berakha by the end of Tuesday (SA and Rema 299:6; MB 19). This applies to the berakhot of Ha-gafen and Ha-mavdil, but the berakhot over fragrances and fire are made only on Saturday night. For it is only on Saturday night that we need to revive the soul with the smell of the fragrances, and the berakha over fire was instituted specifically to remember the fire that Adam discovered on Saturday night. Neither of those is relevant on Sunday.
