HubSpot used to put banners on accounts when they were at 75%, 90%, and 98% of their marketing contact limits. I believe they also emailed admins at these points as well (although I could be mis-remembering that).
HubSpot has discontinued the 75% and 90% notifications without notifying admins about the change. If you were relying on these default HubSpot notifications, you may find yourself in trouble since they disappeared without warning. Being 90% of my marketing contact limit and only able to add 1,000 contacts with 21 days left this month is very different than being 98% and 200 contacts away from the limit.
I would like HubSpot to either reinstate notifications at 75% and 90% or notify the impacted account holders that these notifications were retired and if they want to receive notifications before 98% of their contact limit, they now need to set up custom notifications.