You can switch from monthly to annual payments at any time.
This is how it works
Click on your Avatar in the top right-hand corner and select Billing & Subscriptions:
In the Organisations tab, locate the Organisation you want to update, then click on Upgrade on the right-hand side to switch to annual billing:
Switch the billing toggle from Monthly to Annual, then click on Save and review order to proceed with the payment:
Please note: When switching from monthly to annual billing, any usage from the current billing period carries over. Any unused portion of the monthly subscription is applied as a prorated adjustment to the annual price.