What I’m trying to do
I can’t find a way to change from monthly billing to annual billing. What am I missing?
Things I have tried
I have tried all of the tabs in my account/billing section.
To be sure, I would send an email to Obsidian support 
…
I can’t really find anything in the doc about changing the billing frequency…
Upgrading/downgrading between the available plans yes, but nothing about switching between monthly ↔ yearly.
(I still could have missed the info though 
)
So, I can only guess that you might need to 1st cancel your monthly subscription and then re-subscribe with a yearly payment 
.
In any case, Obsidian support team would provide you with the accurate process to follow 