Q: At tills there are speed points. It takes debit & credit cards. Will we get sin if the customer uses his credit card & says he wants to put it on BUDGET(6 or 12 months-interest will be charged to the customer)?
A: Avoid this. Don’t cooperate in an act that is haraam and forbidden.
وَتَعَاوَنُوا عَلَى الْبِرِّ وَالتَّقْوَىٰ وَلَا تَعَاوَنُوا عَلَى الْإِثْمِ وَالْعُدْوَانِ وَاتَّقُوا اللَّـهَ إِنَّ اللَّـهَ شَدِيدُ الْعِقَابِ ﴿المائدة: ٢﴾