Setting a client to inactive status will cease billing for any one-time or ongoing charges - no recurring fees, storage fees or plans will be assessed after a client is marked 'inactive'. If you want to charge any final outstanding payments, you can charge or record the payment before making the client inactive.
Be sure to check the client's bookings on your calendar(s) to ensure the client doesn't have any overage hours that would have resulted in an additional charge the following month. If the client does have overage hours that should be charged, you can create a one-time fee for those extra hours, to run at midnight tonight, before making the client inactive the following day.
Setting a client to inactive will also release any storage associated with them, so you can provide it to other clients.
The client's future approved bookings will remain on the calendar, but they will not be able to create new bookings on your calendars. Any existing future approved bookings will not be billed while the client is inactive.
The client will remain in your contact list (for reporting reasons), under inactive clients.
If the client becomes active again later on, their past hourly approved bookings from more than 24 hours ago will not be billed. Essentially they will start fresh moving forward.