I found out that in the checkout process, the customer needs to enter his/her zip code to calculate shipping and/or taxes, but if they don't enter a zip code, they can finish the process of buying the item without paying shipping or taxes.
The ZIP code is not associated with shipping - it's used to apply a specific tax to the order. Assuming the seller has their tax table calculations setup, the Zip code is use to determine a specific tax for where you live. For example, a state tax can be 2.9% however, if you live in an area of the state that has it's own additional taxes, your can can be 8.275% after entering the Zip Code. If no Zip code, then the tax is based on the state you reside in. Normally if you don't live in the same state as the seller or merchant, then there's no tax applied. All of this is based on how the seller has his or her tax tables setup according to their state tax regulations.
This user guide has more details concerning setting up tax tables:
The issue that I was talking about is that if the customer doesn't enter any zip code at all, he's gonna pay just the cost of the merchandise as is, because the shopping cart can't add sales taxes (if applicable) or shipping charges (if applicable too).
Then, is there a way to fix the code to obtain the zip code as mandatory?
