US taxes
Shopify helps to automate charging sales taxes. Shopify doesn't remit or file your taxes for you, unless you use Shopify Tax and set up automated filing. You can follow this guide to determine where in the United States you might be responsible for charging taxes. After you know where you're liable for tax, you can configure your store to charge taxes accordingly.
If you need information about 1099-K forms and you use Shopify Payments, then refer to Tax reporting.