Amazon Lightsail EUC1-UnusedStaticIP

If you're being charged for an "Unused Static IP" in Amazon Lightsail, it means there's a static IP address in your account that isn't attached to any instance. This charge occurs because AWS charges $0.005 per hour for static IP addresses that remain unattached to an instance for more than 1 hour.

To resolve this issue and stop the charges, you need to either:

1. Delete (release) the unattached static IP:

• Go to the Lightsail console
• Navigate to the "Networking" tab
• Find the static IP that's not attached to any instance
• Select it and click "Delete" or "Release"

2. Or attach the static IP to an existing Lightsail instance (which would make it free)

It's important to note that even if you don't remember creating a static IP, one might exist in your account. Static IPs that are attached to instances don't incur additional charges, but unattached ones do. Also, make sure to check all AWS regions, as you might have a static IP in a region you don't typically use.

If you've already checked and can't find any unattached static IPs but are still being charged, there might be a delay in the billing system reflecting your changes, or there could be an issue that requires AWS Support assistance.
Sources
I am getting Charged for unattached static IP, But unattached static IP already deleted | AWS re:Post
Billing and account management - Amazon Lightsail