Under your account settings you can manage your current subscription and billing history.
Select Settings in the top green banner and then Subscription Plan Details, only Administrator users can see this option:
You can view your current plan details, or your billing history.
If you have reached your tenancy limit you are also able to purchase a plan. This will allow you to pick what plan will work best for you and upgrade your service as required. You can also update the credit card on file.
Users who do not have Trust Accounting can increase their subscription to 50 or 100 tenancies from this page. For larger plans or trust accounting please contact support for pricing and a promo code.