diff --git a/src/subsidy_type.h b/src/subsidy_type.h
index 8aa6738a42..734a9c87c4 100644
--- a/src/subsidy_type.h
+++ b/src/subsidy_type.h
@@ -8,12 +8,12 @@
 #include "cargo_type.h"
 #include "company_type.h"
 
+/** Struct about subsidies, both offered and awarded */
 struct Subsidy {
-	CargoID cargo_type;
-	byte age;
-	/* from and to can either be TownID, StationID or IndustryID */
-	uint16 from;
-	uint16 to;
+	CargoID cargo_type; ///< Cargo type involved in this subsidy, CT_INVALID for invalid subsidy
+	byte age;           ///< Subsidy age; < 12 is unawarded, >= 12 is awarded
+	uint16 from;        ///< Index of source. Either TownID, IndustryID or StationID, when awarded.
+	uint16 to;          ///< Index of destination. Either TownID, IndustryID or StationID, when awarded.
 };
 
 extern Subsidy _subsidies[MAX_COMPANIES];