The billing amount is calculated from the number of activated users. All Workspace members that has confirmed their account and are not deactivated will count as an active account.

Monthly subscriptions
For monthly subscriptions the change in number of members will not come into effect in terms of billing until the it is time to pay the invoice upfront of the next month.  

Yearly subscriptions
For yearly subscriptions the number of members on a workspace is counted the first of every month. 

Example 1: Team with 12 members starts a yearly subscription on the 1st of January. On the 15th of January 2 new members are added. On the 1st of February an extra invoice would be generated for the charge of 2 members for 11 months.

Example 2: Team with 12 members starts a yearly subscription on the 1st of January. On the 15th of January 2 new members are removed. On the 1st of February the Workspace will be credited for an amount equal to 2 members for 11 months.

When a yearly payment plan is upgraded, the whole sum for the full year is immediately charged minus the balance from the remaining time left on the previous yearly plan. 

If going from a yearly payment plan to a monthly payment plan, the workspace will be credited for the remaining balance for the time remaining on the yearly plan.