Why is WooCommerce not charging tax?

Taxes are switched off, the product's tax status is not Taxable, or no rate row in the product's tax class matches the customer's address. Tick Enable tax rates in Settings > General, set the product to Taxable, and check the rows use two-letter state codes and the right class.

Why does WooCommerce show tax only after the customer enters their ZIP?

A rate row with a ZIP code can only match once the ZIP is known. Set Default customer location to Shop base address or Geolocate so the cart shows an estimate before checkout.

Why is tax zero on local pickup orders in WooCommerce?

Tax is calculated from the shipping address and a pickup order has none. Change Calculate tax based on to billing address, or give the pickup location an address.

More fixes

WooCommerce tax not calculating at checkout

The cart and checkout show Tax: $0.00, or no tax line at all, even though you set up tax rates. Or tax shows for some customers and not others, or only after the address is typed in full. Every order placed like this is one you owe the tax on yourself. WooCommerce adds tax only when taxes are switched on, the product is taxable, and a rate row matches the address it is told to use. Below is a rebuilt example (not a real client), the two checks that find which of those failed, and the fix for each one.

Checkout totals

What the checks found

Check 1: is tax on, and which address does it use

Go to WooCommerce > Settings > General and make sure Enable tax rates and calculations is ticked; without it the Tax tab does not even appear. Then open WooCommerce > Settings > Tax and note two settings: Calculate tax based on (customer shipping address, billing address, or shop base address) and Display prices during cart and checkout. If an automated tax service (WooCommerce Tax, TaxJar, Avalara) is switched on, it replaces your rate tables, so its own connection status matters more than the rows.

Check 2: does a rate row match this product and this address

Open one product that showed no tax and look at Product data > General: Tax status should be Taxable and note its Tax class (Standard, Reduced rate, Zero rate or your own). Then open that class's table under the Tax tab and compare its rows with a real customer address: country code, state code, ZIP or postcode, city. Check one with a real order: in a private window, add that product and enter the address in full at checkout. Note whether tax appears before or after you type the ZIP.

What each answer means

What you see	Cause	Fix
No Tax tab, or Enable tax rates is unticked	Taxes are off for the whole store	Tick it in Settings > General and save, then set up the rates
The Standard rates table is empty, or the rates are in a different class	No row exists for the class the products use	Add the rows to the class your products are in, or set the products to the class that has rows
One product, or all variations of it, show no tax	Tax status is None or Shipping only, or the variation's class is set to Zero rate (variations can override the parent)	Set Tax status to Taxable; for variations set Tax class to Same as parent; bulk edit fixes many at once
Rows exist but nothing matches	The state is typed as a name instead of a code (`California` instead of `CA`), the country code is wrong, ZIPs are in one field without the `;` separator, or a city row restricts it	Use two-letter codes, separate ZIPs with `;` or use ranges like `90001...90899` and wildcards like `902*`; leave City blank unless you need it
Tax is right on shipping orders but zero on local pickup or virtual products	Calculate tax based on is the shipping address, and those orders have none	Set it to billing address, or set the pickup location's address; WooCommerce uses the shop base address for pickup only when told to
Tax shows only after the full address is typed	Normal: WooCommerce cannot match a ZIP row until it has the ZIP. A cart estimate uses the shop base address or none	Set Default customer location to Shop base address or Geolocate so the cart shows an estimate
An automated tax service is on and tax is zero	The service is disconnected, the store address is not one it supports, or the nexus/state is not registered in it	Reconnect it, check its supported countries and add the states where you collect tax; switch it off to fall back to your own table
Tax is missing from shipping cost only	The rate row's Shipping box is unticked, or Shipping tax class is set to a class with no rows	Tick Shipping on the rows that should tax it, or set Shipping tax class to "based on cart items"
You see tax, customers do not	A page cache serves an old checkout, or the customer is a tax-exempt role (some B2B plugins zero it)	Exclude Cart and Checkout from every cache and purge; check the customer's role and any exemption plugin

Check it worked

In a private window, add a taxable product, go to checkout and enter a full address in each state or country you collect tax for. The tax line should match the rate you set. Then place one real order and open it in WooCommerce > Orders: the tax line must be on the order itself, not only on the checkout screen. Orders already placed without tax are not fixed by this; they stay as they were.

What not to do

Do not add the tax into the product price by hand to make it show. You then charge tax on tax once rates start working, and your reports lose the tax figure.
Do not put a single * rate for every country to make a number appear. You will charge tax to customers you should not, which is harder to undo than missing it.
Do not run two tax services at once (a plugin plus your own table). One overrides the other and you cannot tell which number is real.

Which rate you must charge, and where, is a question for your accountant; this page only gets WooCommerce to apply the rates you give it. If you would rather someone else finds and fixes the setup, that is what the box below is for. Related: WooCommerce checkout not working and WooCommerce "No shipping options were found".