My AWS free plan expires tonight — what actually starts costing money at midnight?

The bill is almost never the thing you are using. It is the idle infrastructure that was invisible while credits covered it.

In the order they usually show up:

• NAT Gateway. If your click-through VPC wizard created one — and they usually do — that is around $0.045/hour in us-east-1, roughly $32 a month, before it moves a single byte, plus about $0.045 per GB processed. This is the single most common answer to "why is my toy project forty dollars".
• Public IPv4 addresses. Since 1 February 2024 AWS charges $0.005/hour for every public IPv4 address, in use or idle. About $3.60/month each. That is every public IP on every instance, every Elastic IP you forgot to release, and the one your NAT Gateway needs to exist.
• EBS volumes on stopped instances. Stopping an instance stops compute billing. Storage keeps billing.
• Idle load balancers. Hourly regardless of traffic.

Go and open the VPC console specifically, before anything else. "I did not create a NAT Gateway" and "the wizard created a NAT Gateway" are the same sentence for most people.

Bigger than the bill: on this plan, expiry does not simply flip you to paid.

AWS's free tier FAQ says that when the free plan expires, AWS closes your account and you lose access to your resources and data. There is a window — they retain the data for 90 days after expiry, and you can restore access by upgrading to a paid plan within that period. Miss the 90 days and it is permanently erased.

So if you want anything in that account to still exist tomorrow, upgrade to the paid plan tonight. It takes about two minutes and it is genuinely not the same category of task as "I will sort the billing out at the weekend".

Two things about the timing that catch people out.

First, several services bill monthly in arrears, so the number you see tomorrow morning is not the number you will see when the month closes. Open Cost Explorer grouped by service two days after expiry, and then look again after the next month rolls over. The second look is the honest one.

Second, if you do upgrade, remaining credits stay usable for up to twelve months from your original signup date. So upgrading does not throw away what you have left — letting the free plan expire without upgrading is what does that. Upgrading early is close to free and removes the deadline entirely.

Set the alarm before the deadline, not after the invoice.

AWS Budgets monitoring itself is free. What costs money is action-enabled budgets beyond the first two, at $0.10 per day each, and budget reports at a cent apiece. A plain "email me when spend passes this number" budget is free.

Set two. A $1 budget, which tells you that something is billing at all — that is the signal you actually want in the first 48 hours. And a $10 one, which tells you it is not a rounding error. Route both to an address you read on your phone, not the one you only check at a desk.

If it is genuinely a hobby project, the cheapest fix is architectural rather than administrative.

Delete the VPC-with-NAT arrangement completely. Put the application on Lambda behind an HTTP endpoint, DynamoDB on demand for state, S3 plus CloudFront for anything static. At hobby traffic that sits inside the always-free allowances and, more importantly, there is nothing billed per hour left to forget about.

The pattern behind every one of these threads is the same: the bill that hurts is always something charged per hour that you are not using. Get rid of the per-hour things and the surprise disappears with them.

Easiest fix is to close this account and open a new one with a different card. Free tier resets, no bill, and you get another six months.