The following are a few important masaa-il (rulings) that pertain to people who have many qadhaa salaah to perform.
1. If a person is unable to determine the exact number of salaah that he has missed, he should estimate a number that he is confident will cover the salaah that he has missed.
2. When performing qadhaa salaah, it is necessary for one to specify which qadhaa he is performing. If it is difficult for one to determine the date of the specific salaah (e.g. The Zuhr missed yesterday or the day before) then one may make the following intention, “I am performing qadhaa of the last Zuhr Salaah I missed,” or “I am performing qadhaa of the first Zuhr Salaah from all the Zuhr Salaahs that I have missed.”
However, if a person merely makes the intention, “I am performing qadhaa of Zuhr Salaah” without any further specification of which qadhaa of Zuhr he is performing, the intention will be insufficient and the qadhaa will not be fulfilled. Rather, the salaah will be performed as nafl.
3. To make qadhaa for a Zuhr, ‘Asr or ‘Esha salaah that was missed while on safar (shar‘ee travelling), one will perform two rakaats (even if one is not on safar when performing the qadhaa). Similarly, to make qadhaa of a Zuhr, ‘Asr or ‘Esha salaah that was missed when not on safar, one will perform four rakaats (even if one is performing the qadhaa while on safar).
4. There is no qadhaa for the sunnah and nafl salaahs. However, it is necessary to make qadhaa for the Witr salaah. Hence, for each day, a person will have to perform six qadhaa salaah (Fajr, Zuhr, ‘Asr, Maghrib, ‘Esha and Witr). However, if a person missed the Fajr Salaah and is performing the qadhaa on the same day, then he should perform the sunnah as well as the fardh if it is before zawwaal. If zawwaal has already passed, he will not perform the sunnah. Rather, he will only perform the fardh.