WHMCS 9.1 is here! The latest release is now available and supported for use in production environments, bringing new ways to manage billing, simplify routine maintenance, and build more flexible customer experiences.
Whether you want greater control over invoice handling, an easier way to get started with MarketConnect, or less manual work keeping your installation up to date, WHMCS 9.1 has something for you.
The release also introduces PHP 8.4 support and expands the possibilities for developers building custom checkout experiences through the REST API.

• Manage credit and debit notes with greater flexibility, including configurable invoice immutability.
• Automate maintenance updates with scheduled installations and automatic recovery if an update fails.
• Explore Iris, an optional redesigned navigation experience for the Admin Area.
• Get started with MarketConnect more easily, with account setup and starter credit during eligible upgrades.
• Configure password requirements for administrators and clients.
• Migrate to Stripe Dynamic Payments without requiring clients to re-enter their payment details.
• Run WHMCS on PHP 8.4, with a clear upgrade path.
• Build complete checkout experiences through the REST API, from cart creation to payment and provisioning.
• The legacy PayPal module is no longer included in new 9.1 installs. Existing setups keep working, but we recommend moving to PayPal Payments for the latest features.

Billing workflows can differ from one business to another. WHMCS 9.1 gives you more flexibility in how you manage credit and debit notes and how invoice immutability works.

What's new?

You can now create and manage credit and debit notes across the Admin Area and Client Area. A new sortable Balance column on invoices makes it easier to see the outstanding amount at a glance. Credit and debit notes are also supported in reports and the API.
Invoice immutability is now configurable through General Settings, rather than requiring a configuration file change. You can choose from three modes:

• Immutability on: The default setting, with invoice immutability enabled and credit and debit notes available.
• Immutability off, notes on: Disable immutability while retaining credit and debit note functionality.
• Immutability and notes off: Disable both features.

This gives you more choice over how your billing workflows operate. If your business relies on invoice immutability for its accounting or compliance requirements, you can keep the default setting. If your accounting practices require a different approach, you can select the mode that better suits your needs.

Upgrading from WHMCS 8.13?

Invoice immutability and credit notes are turned on when you upgrade. If you'd prefer to turn them off, see here for how to do it and what to expect compared to 8.13
Keeping your WHMCS installation maintained is important, but remembering to apply every maintenance release can add to your team's workload.
WHMCS 9.1 introduces unattended automatic updates for maintenance releases, helping you keep up with fixes and improvements with less manual intervention. Automatic maintenance updates are enabled by default.

How automatic updates work

You can configure a schedule for maintenance updates. Before applying an update, WHMCS creates a backup of your installation. If the update fails, WHMCS automatically restores that backup.
A new Update History table also records updates, giving you a place to review what has been applied.
There is one important distinction: automatic updates apply to maintenance releases only. Feature releases are not installed automatically.
WHMCS 9.1 introduces Iris, a redesigned navigation experience for the Admin Area.
Iris is optional and is not the default template, so you can explore the new experience when it suits your workflow.

How to try Iris

To switch to Iris, go to Account > My Account.
You can also share your feedback with the WHMCS team through the WHMCS Community.
MarketConnect helps you expand your offering with services like an agentic AI website and app builder, SSL certificates, website security, backups and monitoring, with ordering, provisioning and billing handled inside WHMCS. WHMCS 9.1 makes getting started simpler, whether you're upgrading an existing installation or setting up a new one.

What's new for existing installations?

If your installation isn't linked to a MarketConnect account, WHMCS 9.1 creates one during the upgrade and applies a $50 starter credit, so you can explore the available services at no cost.
You stay in control: nothing changes for your customers until you choose which services to offer and how to price them.

What's new for fresh installations?

The Getting Started Wizard now includes a MarketConnect activation step. It sets up a default selection of products at WHMCS-recommended retail prices:

• Nova on WHMCS Cloud
• SocialBee
• DigiCert RapidSSL

You can review and change your product selection in the Admin Area at any time.

Getting started with MarketConnect

After upgrading, check that your MarketConnect account is connected, then review the products available to you.
Explore MarketConnectPassword policies are an important part of securing an installation. WHMCS 9.1 introduces two additional settings that let you configure password requirements for both administrators and clients.

What's new?

You can set:

• A minimum password length.
• A limit on how many previous passwords can be reused.

These controls help you align your password policies with your security requirements, including relevant requirements under PCI DSS 4.0.1. Compliance depends on your wider environment, so review the PCI DSS requirements that apply to your business.

Where to find the settings

Go to Configuration > System Settings > General Settings > Security.
WHMCS 9.1 makes it easier to move from legacy Stripe modules to Stripe Dynamic Payments, giving you a path to newer payment options without requiring clients to enter their payment details again.

What's new?

The migration path covers the Stripe, Stripe ACH, and Stripe SEPA modules. Clients do not need to re-enter their payment details as part of the migration.
Stripe Dynamic Payments also supports redirect payment methods, including:

• iDEAL
• Bancontact
• BLIK
• Amazon Pay

You can manage supported payment methods through your Stripe Dashboard.
The legacy Stripe modules are deprecated but have not been removed. They continue to work in WHMCS 9.1, allowing you to plan your migration when it suits your business.
WHMCS 9.1 adds support for PHP 8.4 while continuing to support PHP 8.2.
With PHP 8.2 reaching end of life on December 31, 2026, this is a good opportunity to review your environment and plan your move to a supported PHP version.

Upgrade in the right order

Before moving to PHP 8.4, follow this sequence:
1. Upgrade ionCube Loader to version 15.0.0. This is required for WHMCS 9.1.
2. Update WHMCS to version 9.1.
3. Move your environment to PHP 8.4.
Before upgrading PHP, check that your hosting environment and any dependencies you rely on are compatible with the target version.
For developers building custom storefronts or headless commerce experiences, WHMCS 9.1 expands what you can do through the REST API.

What's new?

REST API v2 now supports a more complete checkout journey, including:

• Creating a cart, taking payment, and provisioning a service.
• Paying an existing invoice.
• Managing stored payment methods.

Supported payment gateways, including Stripe Dynamic Payments, can also take payment without redirecting customers to a WHMCS-hosted page.
For teams developing their own storefronts, these capabilities open up more options for shaping the checkout experience while connecting it to WHMCS billing and provisioning workflows.
For endpoint details and supported gateways, see the REST API documentation.
The legacy PayPal module (PayPal Basic) is deprecated and is no longer included in new WHMCS 9.1 installations.
If you're upgrading an existing installation, the legacy module stays in place and continues to work, so nothing changes for you today. For old versions (before 8.13), follow the requirements below for a smooth upgrade. We strongly encourage you to move to PayPal Payments, the newer PayPal integration, which supports the latest PayPal features and is where all future PayPal improvements will go.
PayPal Payments migration guide
Before you upgrade

A few checks can help you prepare:
1. Upgrade ionCube Loader to version 15.0.0.
2. Take a full backup of your files and database before starting.
3. Update WHMCS through Utilities > Update WHMCS, or download WHMCS 9.1 directly.

If you're running the WHMCS 9.1 Beta, you can update to the 9.1 release through the normal update process.

When upgrading an existing installation, the legacy PayPal modules remain in place. If you're upgrading from a version earlier than 8.13 and still use them, first update to the latest 9.0.x release, then to 9.1. If you no longer use them, deactivate and remove them before upgrading. This avoids an admin-area 500 error caused by legacy module files encoded for older PHP versions.

Have questions or feedback? Visit the WHMCS Community to connect with other users and join the conversation.

We look forward to seeing what you build with WHMCS 9.1.