The World Federation One Stop Fiqh

Ruling 753

Nāfilah prayers can be performed in a sitting position even if one does so voluntarily, and [if someone performs these prayers in a sitting position,] it is not necessary to count two rakʿahs as one rakʿah. However, it is better to perform them in a standing position, except for the nāfilah of ʿishāʾ, which based on obligatory precaution must be performed in a sitting position.