diff --git a/packages/server/src/IdentityManager.ts b/packages/server/src/IdentityManager.ts
index 09e9199c4..d7b26597e 100644
--- a/packages/server/src/IdentityManager.ts
+++ b/packages/server/src/IdentityManager.ts
@@ -321,7 +321,7 @@ export class IdentityManager {
         return await this.stripeManager.getAdditionalSeatsProration(subscriptionId, newQuantity)
     }
 
-    public async updateAdditionalSeats(subscriptionId: string, quantity: number, prorationDate: number) {
+    public async updateAdditionalSeats(subscriptionId: string, quantity: number, prorationDate: number, increase: boolean) {
         if (!subscriptionId) return {}
 
         if (!this.stripeManager) {
@@ -330,7 +330,8 @@ export class IdentityManager {
         const { success, subscription, invoice, paymentFailed, paymentError } = await this.stripeManager.updateAdditionalSeats(
             subscriptionId,
             quantity,
-            prorationDate
+            prorationDate,
+            increase
         )
 
         // Fetch product details to get quotas
diff --git a/packages/server/src/StripeManager.ts b/packages/server/src/StripeManager.ts
index dabc2519e..5c80b7260 100644
--- a/packages/server/src/StripeManager.ts
+++ b/packages/server/src/StripeManager.ts
@@ -3,6 +3,9 @@ import { Request } from 'express'
 import { UsageCacheManager } from './UsageCacheManager'
 import { UserPlan } from './Interface'
 import { LICENSE_QUOTAS } from './utils/constants'
+import { InternalFlowiseError } from './errors/internalFlowiseError'
+import { StatusCodes } from 'http-status-codes'
+import logger from './utils/logger'
 
 export class StripeManager {
     private static instance: StripeManager
@@ -359,33 +362,43 @@ export class StripeManager {
         }
     }
 
-    public async updateAdditionalSeats(subscriptionId: string, quantity: number, _prorationDate: number) {
+    public async updateAdditionalSeats(subscriptionId: string, quantity: number, _prorationDate: number, increase: boolean) {
         if (!this.stripe) {
             throw new Error('Stripe is not initialized')
         }
 
         try {
-            const subscription = await this.stripe.subscriptions.retrieve(subscriptionId)
-            const additionalSeatsItem = subscription.items.data.find(
-                (item) => (item.price.product as string) === process.env.ADDITIONAL_SEAT_ID
-            )
-
             // Get the price ID for additional seats if needed
             const prices = await this.stripe.prices.list({
                 product: process.env.ADDITIONAL_SEAT_ID,
                 active: true,
                 limit: 1
             })
-
             if (prices.data.length === 0) {
                 throw new Error('No active price found for additional seats')
             }
 
+            const openInvoices = await this.stripe.invoices.list({
+                subscription: subscriptionId,
+                status: 'open'
+            })
+            const openAdditionalSeatsInvoices = openInvoices.data.filter((invoice) =>
+                invoice.lines?.data?.some((line) => line.price?.id === prices.data[0].id)
+            )
+            logger.info(`openAdditionalSeatsInvoices: ${openAdditionalSeatsInvoices.length}, increase: ${increase}`)
+            if (openAdditionalSeatsInvoices.length > 0 && increase === true)
+                throw new InternalFlowiseError(StatusCodes.PAYMENT_REQUIRED, "Not allow to add seats when there're unsuccessful payment")
+
+            const subscription = await this.stripe.subscriptions.retrieve(subscriptionId)
+            const additionalSeatsItem = subscription.items.data.find(
+                (item) => (item.price.product as string) === process.env.ADDITIONAL_SEAT_ID
+            )
+
             // TODO: Fix proration date for sandbox testing - use subscription period bounds
             const adjustedProrationDate = this.calculateSafeProrationDate(subscription)
 
             // Create an invoice immediately for the proration
-            const updatedSubscription = await this.stripe.subscriptions.update(subscriptionId, {
+            const subscriptionUpdateData: any = {
                 items: [
                     additionalSeatsItem
                         ? {
@@ -396,10 +409,16 @@ export class StripeManager {
                               price: prices.data[0].id,
                               quantity: quantity
                           }
-                ],
-                proration_behavior: 'always_invoice',
-                proration_date: adjustedProrationDate
-            })
+                ]
+            }
+            if (openAdditionalSeatsInvoices.length > 0) {
+                await this.stripe.invoices.voidInvoice(openAdditionalSeatsInvoices[0].id)
+                subscriptionUpdateData.proration_behavior = 'none'
+            } else {
+                ;(subscriptionUpdateData.proration_behavior = 'always_invoice'),
+                    (subscriptionUpdateData.proration_date = adjustedProrationDate)
+            }
+            const updatedSubscription = await this.stripe.subscriptions.update(subscriptionId, subscriptionUpdateData)
 
             // Get the latest invoice for this subscription
             const invoice = await this.stripe.invoices.list({
diff --git a/packages/server/src/enterprise/controllers/organization.controller.ts b/packages/server/src/enterprise/controllers/organization.controller.ts
index fc57184dd..de11fa816 100644
--- a/packages/server/src/enterprise/controllers/organization.controller.ts
+++ b/packages/server/src/enterprise/controllers/organization.controller.ts
@@ -134,7 +134,7 @@ export class OrganizationController {
 
     public async updateAdditionalSeats(req: Request, res: Response, next: NextFunction) {
         try {
-            const { subscriptionId, quantity, prorationDate } = req.body
+            const { subscriptionId, quantity, prorationDate, increase } = req.body
             if (!subscriptionId) {
                 return res.status(400).json({ error: 'Subscription ID is required' })
             }
@@ -144,8 +144,10 @@ export class OrganizationController {
             if (!prorationDate) {
                 return res.status(400).json({ error: 'Proration date is required' })
             }
+            if (increase === undefined) return res.status(StatusCodes.BAD_REQUEST).json({ error: 'Increase is required' })
+
             const identityManager = getRunningExpressApp().identityManager
-            const result = await identityManager.updateAdditionalSeats(subscriptionId, quantity, prorationDate)
+            const result = await identityManager.updateAdditionalSeats(subscriptionId, quantity, prorationDate, increase)
 
             return res.status(StatusCodes.OK).json(result)
         } catch (error) {
diff --git a/packages/ui/src/api/user.js b/packages/ui/src/api/user.js
index 86165ec9c..cc5ff2992 100644
--- a/packages/ui/src/api/user.js
+++ b/packages/ui/src/api/user.js
@@ -18,8 +18,8 @@ const getAdditionalSeatsQuantity = (subscriptionId) =>
 const getCustomerDefaultSource = (customerId) => client.get(`/organization/customer-default-source?customerId=${customerId}`)
 const getAdditionalSeatsProration = (subscriptionId, quantity) =>
     client.get(`/organization/additional-seats-proration?subscriptionId=${subscriptionId}&quantity=${quantity}`)
-const updateAdditionalSeats = (subscriptionId, quantity, prorationDate) =>
-    client.post(`/organization/update-additional-seats`, { subscriptionId, quantity, prorationDate })
+const updateAdditionalSeats = (subscriptionId, quantity, prorationDate, increase) =>
+    client.post(`/organization/update-additional-seats`, { subscriptionId, quantity, prorationDate, increase })
 const getPlanProration = (subscriptionId, newPlanId) =>
     client.get(`/organization/plan-proration?subscriptionId=${subscriptionId}&newPlanId=${newPlanId}`)
 const updateSubscriptionPlan = (subscriptionId, newPlanId, prorationDate) =>
diff --git a/packages/ui/src/views/account/index.jsx b/packages/ui/src/views/account/index.jsx
index 2236e1aed..cd4a57679 100644
--- a/packages/ui/src/views/account/index.jsx
+++ b/packages/ui/src/views/account/index.jsx
@@ -347,7 +347,7 @@ const AccountSettings = () => {
         }
     }
 
-    const handleSeatsModification = async (newSeatsAmount) => {
+    const handleSeatsModification = async (newSeatsAmount, increase) => {
         try {
             setIsUpdatingSeats(true)
 
@@ -358,7 +358,8 @@ const AccountSettings = () => {
             const response = await updateAdditionalSeatsApi.request(
                 currentUser?.activeOrganizationSubscriptionId,
                 newSeatsAmount,
-                prorationInfo.prorationDate
+                prorationInfo.prorationDate,
+                increase
             )
 
             // Check if payment failed but seats were updated (Issue #4 fix)
@@ -1181,7 +1182,7 @@ const AccountSettings = () => {
                         </Button>
                         <Button
                             variant='outlined'
-                            onClick={() => handleSeatsModification(purchasedSeats - seatsQuantity)}
+                            onClick={() => handleSeatsModification(purchasedSeats - seatsQuantity, false)}
                             disabled={
                                 getCustomerDefaultSourceApi.loading ||
                                 !getCustomerDefaultSourceApi.data ||
@@ -1435,7 +1436,7 @@ const AccountSettings = () => {
                         </Button>
                         <Button
                             variant='contained'
-                            onClick={() => handleSeatsModification(seatsQuantity + purchasedSeats)}
+                            onClick={() => handleSeatsModification(seatsQuantity + purchasedSeats, true)}
                             disabled={
                                 getCustomerDefaultSourceApi.loading ||
                                 !getCustomerDefaultSourceApi.data ||