What are the "tax" in cost managemnt ?

The $7.05 tax charge you noticed on July 1st is likely related to** applicable sales tax, VAT, or GST based on your account's billing address and local tax regulations**. AWS typically bills monthly in arrears, meaning this tax was probably applied to your usage from the previous month (June), even if your larger activity began after July 8th. Tax is calculated based on regional laws and is only applied to taxable services, which may include certain AWS offerings or support plans.

You can review the detailed breakdown by visiting the AWS Billing Dashboard, selecting the June bill, and checking the Tax section. If the charge still seems unclear, contacting AWS Support can help provide invoice-specific explanations based on your account’s location.

In AWS Cost Management, "tax" refers to any taxes that are associated with the charges or fees in your cost chart. AWS adds all taxes together as a single component of your costs.

Why is there a Tax spike on the first of the month? Is the customer international? We don't amortize taxes for international customers, so it's expected for them to see a VAT (value added tax) spike on the first of the month. This amount on will continue to grow throughout the month as a percentage of total spend.

Tax calculations are based on your account's address, which determines the applicable tax rates and the appropriate AWS seller of record for your invoices. The tax amount is calculated according to the tax regulations applicable to your location and the specific AWS services you've used.

In Cost Explorer, you can filter specifically by "Tax" to see these charges. Note that when you filter your cost chart, taxes are excluded if you select non-Linked Account filters, but are included if you select Linked Accounts filters. Also, Cost Explorer only displays tax costs when you choose the "Monthly" view.

If you need to manage your tax settings, you can use AWS Tax Settings to handle tax registration numbers, business legal information, and tax exemption certificates if applicable.
Sources
Filtering the data that you want to view - AWS Cost Management
Manage Cloud Invoices and Preferences - AWS Invoices - AWS