Is it permissible to sell an item for its cost price plus an unspecified profit margin (e.g., 'at what my cost is, plus ten')?
Chapter on Selling the Musarrah (Animal with milk retained in udder)
Al-Mughni
Book of Sales
Primary text
Selling an item for its cost price plus an unspecified profit margin, such as stating, 'and profit of ten on every ten dirhams,' is disliked (makruh). This dislike is attributed to Ahmad, Ibn Umar, Ibn Abbas, Masruq, Al-Hasan, 'Ikrimah, Sa'id ibn Jubayr, and 'Ata ibn Yasar. The basis for dislike is the precedent set by Ibn Umar and Ibn Abbas, and the presence of a degree of ambiguity (jahalah). However, this dislike is one of avoidance (tanzeeh), and the sale itself remains valid because the ambiguity can be resolved through calculation, unlike an entirely unknown price derived from an accounting formula.
Supporting text
Sa'id ibn al-Musayyab, Ibn Sirin, Shurayh, Al-Nakha'i, Al-Thawri, Al-Shafi'i, Ibn al-Mundhir, and the People of Opinion permitted this. They argue that since the cost price is known and the profit margin is known, it resembles stating a fixed profit of ten dirhams. Ishaq deemed it impermissible because the price is unknown at the time of the contract.