The first thing is to access our Magento 1.9.X admin or backend panel, once there we go to Control Panel -> Sales -> Taxes -> Tax Zones and Rates.

As we can see, when installing Magento it creates default zones for us, we are going to create our own zones, to do this we click on Add new tax rate.

Now we put a tax identifier, or what is the same, the name to identify it, we can restrict by postal code indicating it, if we put only * it will be for all postal codes, Federated State with * is for all, Country where it will operate and finally the percentage of the rate. Finally, we click on Save rate.

Now in the view we saw before, if it has been created correctly, we will see the identifier of the created product.

Now we are going to create the tax rule, for this we go to Sales -> Taxes -> Manage Tax Rules.

In this new view, we can see that we do not have any tax rule created, so we go to Add new tax rule.

In this new view, we can see that it asks us for:

Name: It is the one that will appear for us to select in the product when we enter it.

Customer tax class: Refers to the tax class that applies to the customer or group of customers.

Product tax class: It is the identifying name that will be shown to us when we create a product, to create them we go to Sales -> Taxes -> Customer Tax Classes.

Tax rate: We select the rate that applies for this rule.

With this we can now click on Save Rule and we would have created our new rule, as can be seen in the following image.

To simply review that it has been created and how it looks when creating the product, we go to Catalog -> Manage Products.

Here we click on Add product and in the Prices or Price tab we will see the rule created with the name we entered.