Why the option is unavailable
Klaviyo's help center is direct about it: auto-downgrade is only for the Profiles & Email plan, it's based on active profile count, and it can be used with Flexible overages or None, not with auto-upgrade. When you first buy a Profiles & Email plan, Automatically upgrade is selected by default. Most accounts never change it, so auto-downgrade stays off limits.
The fix
Change the email upgrade preference
Select your account name in the lower left and go to Billing > Preferences. Switch the email preference from Automatically upgrade to Flexible overages or None, and click Update.
Select Auto-downgrade profiles
In the Profiles auto-downgrade section, select Auto-downgrade profiles.
Click that section's Update button
The section has its own Update button. The setting isn't saved until you click it.
Flexible overages or None?
This preference is about email sends, not profiles. With None, Klaviyo stops sending when you hit your plan's send limit, until you upgrade, use flexible overages, or the billing cycle renews. With Flexible overages, sending continues past the limit and the extra is billed instead of moving you up a tier. Check Klaviyo's article for current overage terms before you pick. If you never get near your send limit, None costs nothing.
Still can't turn it on?
- Check you're on the Profiles & Email plan. Auto-downgrade isn't offered on other plan types.
- Check that the email preference change saved. Reload Billing > Preferences and look again.
- If the option is still unavailable, Klaviyo's help center says to contact Klaviyo support.
What happens once it's on
Klaviyo checks your active profile count 24 hours before your billing cycle ends. If the count fits a lower tier, you're moved down. Turning off auto-upgrade for sends doesn't stop upgrades driven by profile count, and an upgrade before the downgrade takes effect cancels it. The setting lets you move down. You still have to get your count under the lower tier's ceiling before that check. The calculator above shows how many profiles that takes.