Fathom billing occurs once a month and you are able to change your subscription plan at any time before the next billing date.
Upgrades will occur automatically to ensure you remain on
the optimal plan as you add companies to your Fathom account.
Downgrades do
not occur automatically as users often wish to retain available company slots even when they delete or remove a company from their Fathom account. Therefore, if you delete or remove a company to decrease
the amount of billable companies on your Fathom account, you will want to change your subscription plan as well.
Learn more here.