diff --git a/src/economy_base.h b/src/economy_base.h
--- a/src/economy_base.h
+++ b/src/economy_base.h
@@ -48,7 +48,17 @@ struct CargoPayment : CargoPaymentPool::
 	void SetCargo(CargoID ct) { this->ct = ct; }
 };
 
+/**
+ * Iterate over all cargo payments from a given start position.
+ * @param var The variable used for iterating.
+ * @param start The start of the iteration.
+ */
 #define FOR_ALL_CARGO_PAYMENTS_FROM(var, start) FOR_ALL_ITEMS_FROM(CargoPayment, cargo_payment_index, var, start)
+
+/**
+ * Iterate over all cargo payments.
+ * @param var The variable used for iterating.
+ */
 #define FOR_ALL_CARGO_PAYMENTS(var) FOR_ALL_CARGO_PAYMENTS_FROM(var, 0)
 
 #endif /* ECONOMY_BASE_H */