diff --git a/indexer/services/comlink/__tests__/controllers/api/v4/fills-controller.test.ts b/indexer/services/comlink/__tests__/controllers/api/v4/fills-controller.test.ts
index a1a8857009..00eb2283af 100644
--- a/indexer/services/comlink/__tests__/controllers/api/v4/fills-controller.test.ts
+++ b/indexer/services/comlink/__tests__/controllers/api/v4/fills-controller.test.ts
@@ -107,6 +107,7 @@ describe('fills-controller#V4', () => {
         orderId: ethOrder.id,
         createdAt: ethFill.createdAt,
         createdAtHeight: ethFill.createdAtHeight,
+        subaccountNumber: defaultSubaccountNumber,
       };
 
       // Only the ETH-USD order should be returned
diff --git a/indexer/services/comlink/public/api-documentation.md b/indexer/services/comlink/public/api-documentation.md
index f1c932f218..46cbc57c80 100644
--- a/indexer/services/comlink/public/api-documentation.md
+++ b/indexer/services/comlink/public/api-documentation.md
@@ -580,7 +580,8 @@ fetch('https://dydx-testnet.imperator.co/v4/fills?address=string&subaccountNumbe
       "createdAt": "string",
       "createdAtHeight": "string",
       "orderId": "string",
-      "clientMetadata": "string"
+      "clientMetadata": "string",
+      "subaccountNumber": 0
     }
   ]
 }
@@ -2598,7 +2599,8 @@ This operation does not require authentication
   "createdAt": "string",
   "createdAtHeight": "string",
   "orderId": "string",
-  "clientMetadata": "string"
+  "clientMetadata": "string",
+  "subaccountNumber": 0
 }
 
 ```
@@ -2620,6 +2622,7 @@ This operation does not require authentication
 |createdAtHeight|string|true|none|none|
 |orderId|string|false|none|none|
 |clientMetadata|string|false|none|none|
+|subaccountNumber|number(double)|true|none|none|
 
 ## FillResponse
 
@@ -2644,7 +2647,8 @@ This operation does not require authentication
       "createdAt": "string",
       "createdAtHeight": "string",
       "orderId": "string",
-      "clientMetadata": "string"
+      "clientMetadata": "string",
+      "subaccountNumber": 0
     }
   ]
 }
diff --git a/indexer/services/comlink/public/swagger.json b/indexer/services/comlink/public/swagger.json
index a3ae9dbf22..e7ca71e256 100644
--- a/indexer/services/comlink/public/swagger.json
+++ b/indexer/services/comlink/public/swagger.json
@@ -409,6 +409,10 @@
           },
           "clientMetadata": {
             "type": "string"
+          },
+          "subaccountNumber": {
+            "type": "number",
+            "format": "double"
           }
         },
         "required": [
@@ -422,7 +426,8 @@
           "size",
           "fee",
           "createdAt",
-          "createdAtHeight"
+          "createdAtHeight",
+          "subaccountNumber"
         ],
         "type": "object",
         "additionalProperties": false
diff --git a/indexer/services/comlink/src/controllers/api/v4/fills-controller.ts b/indexer/services/comlink/src/controllers/api/v4/fills-controller.ts
index eed5255103..52e0d6a0a2 100644
--- a/indexer/services/comlink/src/controllers/api/v4/fills-controller.ts
+++ b/indexer/services/comlink/src/controllers/api/v4/fills-controller.ts
@@ -90,7 +90,7 @@ class FillsController extends Controller {
 
     return {
       fills: fills.map((fill: FillFromDatabase): FillResponseObject => {
-        return fillToResponseObject(fill, clobPairIdToMarket);
+        return fillToResponseObject(fill, clobPairIdToMarket, subaccountNumber);
       }),
     };
   }
@@ -139,13 +139,16 @@ router.get(
       createdBeforeOrAt,
     }: FillRequest = matchedData(req) as FillRequest;
 
+    // The schema checks allow subaccountNumber to be a string, but we know it's a number here.
+    const subaccountNum : number = +subaccountNumber;
+
     // TODO(DEC-656): Change to using a cache of markets in Redis similar to Librarian instead of
     // querying the DB.
     try {
       const controller: FillsController = new FillsController();
       const response: FillResponse = await controller.getFills(
         address,
-        subaccountNumber,
+        subaccountNum,
         market,
         marketType,
         limit,
diff --git a/indexer/services/comlink/src/request-helpers/request-transformer.ts b/indexer/services/comlink/src/request-helpers/request-transformer.ts
index 1fe32aa721..1b1e69e982 100644
--- a/indexer/services/comlink/src/request-helpers/request-transformer.ts
+++ b/indexer/services/comlink/src/request-helpers/request-transformer.ts
@@ -134,6 +134,7 @@ export function assetPositionToResponseObject(
 export function fillToResponseObject(
   fill: FillFromDatabase,
   marketsByClobPairId: MarketAndTypeByClobPairId,
+  subaccountNumber: number,
 ): FillResponseObject {
   return {
     id: fill.id,
@@ -149,6 +150,7 @@ export function fillToResponseObject(
     createdAtHeight: fill.createdAtHeight,
     orderId: fill.orderId,
     clientMetadata: fill.clientMetadata,
+    subaccountNumber,
   };
 }
 
diff --git a/indexer/services/comlink/src/types.ts b/indexer/services/comlink/src/types.ts
index c61fdd55fc..57c4e092e0 100644
--- a/indexer/services/comlink/src/types.ts
+++ b/indexer/services/comlink/src/types.ts
@@ -129,6 +129,7 @@ export interface FillResponseObject {
   createdAtHeight: string,
   orderId?: string,
   clientMetadata?: string,
+  subaccountNumber: number,
 }
 
 /* ------- TRANSFER TYPES ------- */