A couple of possible reasons:
If you didn't cancel the autopay from your dashboard and your tenant didn't cancel their plan in their Split Pay account, the autopay stayed active and charged them as scheduled. Physically moving out doesn't stop the autopay on its own.
If the payment was already in flight when the cancellation was attempted, it couldn't be stopped — ACH payments take 3-5 business days to fully settle once they start processing.
We're not able to issue refunds once a payment has begun processing or has settled. If a refund is owed, that's something to work out directly with your tenant.
To prevent this on the next cycle: cancel the autopay from your dashboard, or ask your tenant to cancel their plan (in their Split Pay profile, under Plan Details → Cancel Plan), as soon as you're ready to end it — ideally well before the next scheduled payment date.
Note: This applies to tenants who pay you directly through Split Pay. Portal autopays follow your portal's own rules.