We have set up a forum for our company, but the approval process takes much longer than anticipated. Paying for a forum that nobody uses yet is a little pointless, but we also don't want to lose the work that has been put into it so far (customization, user groups, rights etc.). Is there a way to set a forum to inactive so it cannot be accessed by anyone  including the admins and pausing the payment, and then reactivate it two or three months later and resume payment without losing any of the data in between?

Are you self hosted or hosted in cloud?

Cloud.

We unfortunately do not have a mechanism to pause a cloud package, however, should you let the service expire, you have 60 days to reactivate before service is permanently terminated. 

How do I let the service expire? Just simply by removing the payment information and then resume payment before 60 days have passed?

If you remove the payment method then of course it will indeed expire. You would need to let us know before the 60 days to generate a new invoice for you. Note, I would advise ensuring you do that a few days before, as once its gone, its gone. 

Okay, makes sense. Thanks for your help, it's much appreciated!