Restaurant Tips

Assalamualaikum,My question is regarding tips at restaurants. Does Islam have anything to say on the topic of tips? If we don't tip, is it sinful? Some people tip $20-25 for their tip, is this permissible even though they are going through difficult times financially?JazakAllah khairan, I am eagerly awaiting your reply.

بِسْمِ اللهِ الرَّحْمٰنِ الرَّحِيْمِ
الجواب وباللہ التوفیق
الجواب وبالله التوفيق Giving a tip is a courteous thing to do and is given out of satisfaction for a worker’s services. However there will be no sin if one does not discharge a tip.       واللہ اعلم  بالصواب

Fatawa ID: 783

فقط واللہ اعلم بالصواب