Daily Halacha
Make Up!
It has already been explained in Chapter 18 that if you allowed the time of tefillah to pass intentionally, without davening, there is no compensation. But if it was unintentional, or due to something beyond your control, that you did not daven, or if you did daven, but erred in your tefillah in a way that requires that you repeat the tefillah, then you may compensate for it following the next tefillah. You must first daven the tefillah that is due at that time and only afterwards the make-up tefillah, for example: if you did not daven the Shacharis tefillah, then when the time for Mincha arrives, you first daven a tefilah for Mincha, followed by Tachanun, and immediately afterwards you should say Ashrei, and then daven another Shemoneh Esrei for the sake of the omitted Shacharis. Similarly if you omitted Mincha, then you should first daven Maariv, and then pause only for the time it takes to walk four amos, do not say Ashrei, but, immediately, daven Shemoneh Esrei for the sake of the omitted Mincha. Similarly if you omitted Maariv, then after Shacharis you should say Tachanun and Ashrei and then daven Shemoneh Esrei for the sake of Maariv. After that you would say Lamenatzeiach and Uva letzion, etc. You may not eat until you also complete the make-up tefillah, which is for the sake of Maariv. (KSA 21:1)