السلام عليكم ورحمة الله وبركاته أحسن الله إليكم What is the ruling on using payment apps like Tabby and Tamara in Saudi Arabia, which allow payments in instalments instead of paying in full? Is it permissible to use them if there are no apparent extra charges? جزاكم الله خيرا

Of course, I cannot give an answer until I know exactly what they do. What if they have late fees, for example? Instead of paying a certain amount of money on time, you are going to pay more if you are late. This is now forbidden interest riba, and I do not know how these companies that you have named deal with these issues and what their services are.