If a fardh act, e.g. Ruku' or one Sajdah is mistakenly omitted, what should be done?

Answer

If a Fardh is omitted in Salaat, then it should be compensated by performing it as soon as one recalls the omission. Then Sajdah Sahw has to be made. If a Waajib is missed out, then there is no compensation besides Sajdah Sahw. The omitted Waajib act does not have to be repeated later. Only Sajdah Sahw should be made.