[jedberg]

Are they monthly invoices? Most billing systems will bill monthly recurring bills that have an anniversary of 28, 29, 30, or 31 on Feb 28. Maybe your system was actually doing the right thing and putting only 29, 30, and 31 on Feb 29.

[mrlucax]

Yes! It's anniversary based. What went wrong actually was the notification part. As Feb 29 was not an expected anniversary, it didn't schedule any notification to be sent.