Can I submit an old premium bill?

It depends on how far back the bill goes and whether you're on Auto-Reimbursement or submitting manually.

If you're on Auto-Reimbursement

Auto-Reimbursement isn't retroactive -- it only covers months after it's been set up and approved. If you had a health plan active before Auto-Reimbursement started, those earlier months aren't automatically picked up.

What to do instead

Use the One-Time Reimbursement feature to manually request payment for a prior month's premium. This is subject to your employer admin's approval and StretchDollar's reimbursement window, so it's best to submit it as soon as you can rather than waiting.

See How do I submit a one-time reimbursement? for the steps, and Auto-Reimbursement Isn't Retroactive: Getting Paid for Prior Months for more detail on how this works.