Unexpected AWS charges (and how to fix it)

Unexpected AWS charges usually happen when something in your account starts using more resources than you realised. This could be a server left running, storage growing, logs building up, traffic increasing, or a service charging in the background.

The confusing part is that AWS charges can appear even when you did not knowingly launch anything new. Because AWS is usage-based, background activity can still increase your bill.

For example, an old test environment, forgotten EC2 instance, NAT Gateway, CloudWatch log group, or unused storage volume can keep creating charges until you find and fix it.

Explain my AWS bill now
Quick answer: Unexpected AWS charges are usually caused by running resources, storage, logs, data transfer, NAT Gateway usage, backups, or services left active by mistake.

Why unexpected AWS charges happen

AWS charges for active usage. That means you can be charged for resources that are still running, even if you are not actively using them.

A common example is creating something for testing, forgetting about it, and then seeing the cost appear later on your bill.

This is why unexpected charges often feel similar to an unexpected AWS bill or an AWS bill that is too high.

First things to check

  • EC2 instances still running
  • Unattached EBS volumes
  • Old snapshots or backups
  • CloudWatch logs growing
  • NAT Gateway traffic
  • Elastic IPs not attached
  • Idle load balancers

Common services behind unexpected AWS charges

Most surprise AWS charges come from a few services that keep billing in the background.

  • EC2: instances running longer than expected
  • EBS: volumes and snapshots kept after deleting instances
  • S3: storage, requests, retrievals, or old files
  • CloudWatch: logs retained for too long
  • RDS: database instances, backups, or storage growth
  • NAT Gateway: outbound traffic from private subnets
  • Data transfer: traffic leaving AWS or moving between regions

These costs can also make AWS feel expensive this month or cause your AWS bill to keep increasing.

How to find the charge

  1. Open AWS Cost Explorer
  2. Set the date range to the month with the charge
  3. Group costs by service
  4. Find the service with the biggest increase
  5. Check region and usage type
  6. Look for resources still running

Why charges can appear suddenly

Some charges are not obvious until the bill updates. You might not notice them day by day, but they can become clear once AWS groups the cost by service.

This can happen when traffic increases, logs grow quickly, backups are created, or an old resource keeps running longer than expected.

A sudden charge may also look like an unexpectedly massive AWS bill.

Example: unexpected AWS charges

  • Expected bill: £80
  • Actual bill: £245
  • EC2 +£95 because a test instance was left running
  • EBS +£28 because old storage volumes were still attached
  • CloudWatch +£22 because logs were kept too long
  • NAT Gateway +£35 because private resources sent outbound traffic
  • Fix: stop unused instances, delete unattached volumes, reduce log retention, and review NAT Gateway usage

How to fix unexpected AWS charges

The safest way to fix unexpected AWS charges is to identify the exact service first, then take targeted action.

  • Stop EC2 instances you no longer need
  • Delete unattached EBS volumes
  • Remove old snapshots and backups
  • Reduce CloudWatch log retention
  • Review NAT Gateway and data transfer usage
  • Check S3 storage and lifecycle rules
  • Remove idle load balancers and unused test environments

Do not randomly delete resources without checking what they are used for. The goal is to remove waste without breaking your application.

Use ExplainMyBill.ai

ExplainMyBill.ai helps you understand unexpected AWS charges by comparing your costs and explaining what changed in plain English.

Instead of digging through AWS billing dashboards, it shows which services caused the increase and what you should check next.

Explain my AWS bill now

FAQ

Why did I get unexpected AWS charges?

You were likely charged for running resources, storage, logs, backups, data transfer, or services left active in your AWS account.

Can AWS charge me even if I am not using it?

Yes. If resources are still running or stored in your account, AWS can continue charging for them.

What causes surprise AWS costs?

Common causes include EC2, EBS volumes, snapshots, CloudWatch logs, NAT Gateway, data transfer, S3 storage, and RDS backups.

How do I find unexpected AWS charges?

Use AWS Cost Explorer, group by service, compare dates, then check the region and usage type for the service that increased.

How do I stop unexpected AWS charges?

Find the service causing the charge, then stop unused resources, delete old storage, reduce logs, or remove unnecessary infrastructure.