diff --git a/src/Center/center.schema.ts b/src/Center/center.schema.ts
index b9a015a..01f2231 100644
--- a/src/Center/center.schema.ts
+++ b/src/Center/center.schema.ts
@@ -215,10 +215,7 @@ export class CenterSchema extends PothosSchema {
               throw new Error('Center not found');
             }
             // check if center is already approved or rejected
-            if (
-              center.centerStatus === CenterStatus.APPROVED ||
-              center.centerStatus === CenterStatus.REJECTED
-            ) {
+            if (center.centerStatus !== CenterStatus.PENDING) {
               throw new Error('Center is already approved or rejected');
             }
             // find center owner and promote to staff
diff --git a/src/CenterStaff/centerstaff.schema.ts b/src/CenterStaff/centerstaff.schema.ts
index bf865b0..8e7dd73 100644
--- a/src/CenterStaff/centerstaff.schema.ts
+++ b/src/CenterStaff/centerstaff.schema.ts
@@ -7,12 +7,15 @@ import {
 } from '@smatch-corp/nestjs-pothos';
 import { Builder } from '../Graphql/graphql.builder';
 import { PrismaService } from '../Prisma/prisma.service';
-
+import { MailService } from '../Mail/mail.service';
+import { JwtUtils } from '../common/utils/jwt.utils';
 @Injectable()
 export class CenterStaffSchema extends PothosSchema {
   constructor(
     @Inject(SchemaBuilderToken) private readonly builder: Builder,
     private readonly prisma: PrismaService,
+    private readonly mailService: MailService,
+    private readonly jwtUtils: JwtUtils,
   ) {
     super();
   }
@@ -121,6 +124,45 @@ export class CenterStaffSchema extends PothosSchema {
           });
         },
       }),
+      inviteCenterStaff: t.prismaField({
+        type: this.centerStaff(),
+        description: 'Invite a new center staff member.',
+        args: {
+          email: t.arg({ type: 'String', required: true }),
+        },
+        resolve: async (query, root, args, ctx, info) => {
+          return this.prisma.$transaction(async (prisma) => {
+            // get centerId by user id from context
+            const userId = ctx.me.id;
+            if (!userId) {
+              throw new Error('User ID is required');
+            }
+            // get centerId by user id
+            const center = await prisma.center.findUnique({
+              where: { centerOwnerId: userId },
+            });
+            if (!center) {
+              throw new Error('Center not found');
+            }
+            // build signature
+            const token = this.jwtUtils.signTokenRS256(
+              { centerId: center.id, email: args.email },
+              '1d',
+            );
+            // build invite url
+            const inviteUrl = `${process.env.CENTER_BASE_URL}/invite?token=${token}`;
+            // mail to user with params centerId, email
+            await this.mailService.sendEmail(
+              args.email,
+              'Invite to center',
+              `You are invited to join the center ${center.name}.
+              Please click the link below to join the center:
+              ${inviteUrl}`,
+            );
+            return null;
+          });
+        },
+      }),
     }));
   }
 }
diff --git a/src/Graphql/graphql.builder.ts b/src/Graphql/graphql.builder.ts
index 0cd4f35..26cbd3f 100644
--- a/src/Graphql/graphql.builder.ts
+++ b/src/Graphql/graphql.builder.ts
@@ -33,6 +33,7 @@ export interface SchemaContext {
   generator: PrismaCrudGenerator<BuilderTypes>;
 }
 
+// extend prisma types to contain string type
 export interface SchemaBuilderOption {
   Context: SchemaContext;
   PrismaTypes: PrismaTypes;
diff --git a/src/Service/service.schema.ts b/src/Service/service.schema.ts
index 923f530..9a0a1e3 100644
--- a/src/Service/service.schema.ts
+++ b/src/Service/service.schema.ts
@@ -241,10 +241,7 @@ export class ServiceSchema extends PothosSchema {
             if (!service) {
               throw new Error('Service not found');
             }
-            if (
-              service.status === ServiceStatus.APPROVED ||
-              service.status === ServiceStatus.REJECTED
-            ) {
+            if (service.status !== ServiceStatus.PENDING) {
               throw new Error('Service is already approved or rejected');
             }
             // update service status
diff --git a/src/common/common.module.ts b/src/common/common.module.ts
index 2553cd4..fd288a3 100644
--- a/src/common/common.module.ts
+++ b/src/common/common.module.ts
@@ -1,9 +1,11 @@
-import { Module } from '@nestjs/common';
-import { CommonGraphqlError } from './graphql/common.graphql.error';
+import { Global, Module } from '@nestjs/common';
 
+import { CommonGraphqlError } from './graphql/common.graphql.error';
+import { JwtUtils } from './utils/jwt.utils';
+@Global()
 @Module({
   imports: [],
-  providers: [CommonGraphqlError],
-  exports: [CommonGraphqlError],
+  providers: [CommonGraphqlError, JwtUtils],
+  exports: [CommonGraphqlError, JwtUtils],
 })
 export class CommonModule {}
diff --git a/src/common/utils/jwt.utils.ts b/src/common/utils/jwt.utils.ts
new file mode 100644
index 0000000..af2b7c4
--- /dev/null
+++ b/src/common/utils/jwt.utils.ts
@@ -0,0 +1,29 @@
+import { sign, verify } from 'jsonwebtoken';
+
+import { Injectable } from '@nestjs/common';
+
+@Injectable()
+export class JwtUtils {
+  signToken(payload: string, expiresIn: string) {
+    return sign(payload, process.env.JWT_SECRET!, { expiresIn });
+  }
+  //eslint-disable-next-line @typescript-eslint/no-explicit-any
+  signTokenRS256(payload: any, expiresIn: string) {
+    const privateKey = process.env.JWT_RS256_PRIVATE_KEY!;
+    return sign(payload, privateKey, {
+      algorithm: 'RS256',
+      expiresIn,
+    });
+  }
+
+  verifyTokenRS256(token: string) {
+    const publicKey = process.env.JWT_RS256_PUBLIC_KEY!;
+    return verify(token, publicKey, {
+      algorithms: ['RS256'],
+    });
+  }
+
+  verifyToken(token: string) {
+    return verify(token, process.env.JWT_SECRET!);
+  }
+}