What do I do in the Gift Certificate Liability account with vouchers that have expired (not redeemed)?

Hello, @s_heagney.

I'd be happy to help share some insights about your expired vouchers. 

You can either delete the transaction for the Gift certificate or create a Journal Entry to zero the liability for the expiration dates. I'd suggest reaching out to your accountant on what would be the best option to do this.

If you need some related references, you can check the following links below.

Create a journal entry

Void or delete an invoice, bill, or other transactions

This should set you on the right track. If you have other questions about your gift certificates, do let me know. I'm here to keep helping.