diff --git a/package.json b/package.json
index 67d6e4c..3bd46ca 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "bybit-api",
-  "version": "3.9.0",
+  "version": "3.9.1",
   "description": "Complete & robust Node.js SDK for Bybit's REST APIs and WebSockets, with TypeScript & strong end to end tests.",
   "main": "lib/index.js",
   "types": "lib/index.d.ts",
diff --git a/src/rest-client-v5.ts b/src/rest-client-v5.ts
index fce2c9e..d3fb058 100644
--- a/src/rest-client-v5.ts
+++ b/src/rest-client-v5.ts
@@ -38,6 +38,7 @@ import {
   CreateSubMemberParamsV5,
   CreateSubMemberResultV5,
   CursorListV5,
+  DeleteSubMemberParamsV5,
   DeliveryPriceV5,
   DeliveryRecordV5,
   DepositAddressResultV5,
@@ -1251,9 +1252,8 @@ export class RestClientV5 extends BaseRestClient {
   /**
    * Create a new sub user id. Use master user's api key only.
    *
-   * The API key must own one of permissions will be allowed to call the following API endpoint.
-   *
-   * master API key: "Account Transfer", "Subaccount Transfer", "Withdrawal"
+   * The API key must have one of the permissions to be allowed to call the following API endpoint.
+   * - master API key: "Account Transfer", "Subaccount Transfer", "Withdrawal"
    */
   createSubMember(
     params: CreateSubMemberParamsV5,
@@ -1264,9 +1264,8 @@ export class RestClientV5 extends BaseRestClient {
   /**
    * To create new API key for those newly created sub UID. Use master user's api key only.
    *
-   * TIP
-   * The API key must own one of permissions will be allowed to call the following API endpoint.
-   * master API key: "Account Transfer", "Subaccount Transfer", "Withdrawal"
+   * TIP: The API key must have one of the permissions to be allowed to call the following API endpoint.
+   * - master API key: "Account Transfer", "Subaccount Transfer", "Withdrawal"
    */
   createSubUIDAPIKey(
     params: CreateSubApiKeyParamsV5,
@@ -1286,9 +1285,8 @@ export class RestClientV5 extends BaseRestClient {
   /**
    * Froze sub uid. Use master user's api key only.
    *
-   * TIP: The API key must own one of the following permissions will be allowed to call the following API endpoint.
-   *
-   * master API key: "Account Transfer", "Subaccount Transfer", "Withdrawal"
+   * TIP: The API key must have one of the permissions to be allowed to call the following API endpoint.
+   * - master API key: "Account Transfer", "Subaccount Transfer", "Withdrawal"
    */
   setSubUIDFrozenState(
     subuid: number,
@@ -1310,9 +1308,8 @@ export class RestClientV5 extends BaseRestClient {
   /**
    * Modify the settings of a master API key. Use the API key pending to be modified to call the endpoint. Use master user's API key only.
    *
-   * TIP: The API key must own one of the permissions to call the following API endpoint.
-   *
-   * Master API key: "Account Transfer", "Subaccount Transfer", "Withdrawal"
+   * TIP: The API key must have one of the permissions to be allowed to call the following API endpoint.
+   * - master API key: "Account Transfer", "Subaccount Transfer", "Withdrawal"
    */
   updateMasterApiKey(
     params: UpdateApiKeyParamsV5,
@@ -1336,8 +1333,9 @@ export class RestClientV5 extends BaseRestClient {
   /**
    * Delete the api key of master account. Use the api key pending to be delete to call the endpoint. Use master user's api key only.
    *
-   * TIP: The API key must own one of permissions will be allowed to call the following API endpoint.
-   *      master API key: "Account Transfer", "Subaccount Transfer", "Withdrawal"
+   * TIP:
+   * The API key must have one of the permissions to be allowed to call the following API endpoint.
+   * - master API key: "Account Transfer", "Subaccount Transfer", "Withdrawal"
    *
    * DANGER: BE CAREFUL! The API key used to call this interface will be invalid immediately.
    */
@@ -1348,9 +1346,9 @@ export class RestClientV5 extends BaseRestClient {
   /**
    * Delete the api key of sub account. Use the api key pending to be delete to call the endpoint. Use sub user's api key only.
    *
-   * TIP
-   * The API key must own one of permissions will be allowed to call the following API endpoint.
-   * sub API key: "Account Transfer"
+   * TIP:
+   * The API key must have one of the permissions to be allowed to call the following API endpoint.
+   * - sub API key: "Account Transfer"
    *
    * DANGER: BE CAREFUL! The API key used to call this interface will be invalid immediately.
    */
@@ -1358,6 +1356,19 @@ export class RestClientV5 extends BaseRestClient {
     return this.postPrivate('/v5/user/delete-sub-api');
   }
 
+  /**
+   * Delete a sub UID. Before deleting the UID, please make sure there are no assets.
+   * 
+   * TIP:
+   * The API key must have one of the permissions to be allowed to call the following API endpoint.
+   * - master API key: "Account Transfer", "Subaccount Transfer", "Withdrawal"
+   */
+  deleteSubMember(
+    params: DeleteSubMemberParamsV5,
+  ): Promise<APIResponseV3WithTime<{}>> {
+    return this.postPrivate('/v5/user/del-submember', params);
+  }
+
   /**
    *
    ****** Spot Leverage Token APIs
diff --git a/src/types/request/v5-asset.ts b/src/types/request/v5-asset.ts
index b20402d..9da70da 100644
--- a/src/types/request/v5-asset.ts
+++ b/src/types/request/v5-asset.ts
@@ -124,18 +124,3 @@ export interface WithdrawParamsV5 {
   forceChain?: number;
   accountType?: 'SPOT' | 'FUND';
 }
-
-export interface CreateSubMemberParamsV5 {
-  username: string;
-  password?: string;
-  /**
-   * 1: normal, 6: custodial
-   */
-  memberType: 1 | 6;
-  /**
-   * 0: quick login disabled (default), 1: quick login enabled
-   */
-  switch?: 0 | 1;
-  isUta?: boolean;
-  note?: string;
-}
diff --git a/src/types/request/v5-user.ts b/src/types/request/v5-user.ts
index f1d60cf..c8a3f5e 100644
--- a/src/types/request/v5-user.ts
+++ b/src/types/request/v5-user.ts
@@ -1,5 +1,21 @@
 import { PermissionsV5 } from '../v5-shared';
 
+
+export interface CreateSubMemberParamsV5 {
+  username: string;
+  password?: string;
+  /**
+   * 1: normal, 6: custodial
+   */
+  memberType: 1 | 6;
+  /**
+   * 0: quick login disabled (default), 1: quick login enabled
+   */
+  switch?: 0 | 1;
+  isUta?: boolean;
+  note?: string;
+}
+
 export interface CreateSubApiKeyParamsV5 {
   subuid: number;
   note?: string;
@@ -19,3 +35,7 @@ export interface UpdateSubApiKeyUpdateParamsV5 {
   ips?: string[];
   permissions: PermissionsV5;
 }
+
+export interface DeleteSubMemberParamsV5 {
+  subMemberId: string;
+}
diff --git a/test/v5/private.write.test.ts b/test/v5/private.write.test.ts
index 13376a0..ffbf324 100644
--- a/test/v5/private.write.test.ts
+++ b/test/v5/private.write.test.ts
@@ -409,6 +409,18 @@ describe('Private WRITE V5 REST API Endpoints', () => {
       });
     });
 
+    it.skip('deleteSubMember()', async () => {
+      expect(
+        await api.deleteSubMember({
+          subMemberId: '1',
+        }),
+      ).toMatchObject({
+        // ...successResponseObjectV3(),
+        // retMsg: '',
+        retCode: API_ERROR_CODE.SUB_USER_NOT_FOUND,
+      });
+    });
+
     it('setSubUIDFrozenState()', async () => {
       expect(await api.setSubUIDFrozenState(0, 1)).toMatchObject({
         // ...successResponseObjectV3(),