How do I pay import taxes/customs?
If you are in the United States typically import taxes are paid by the supplier before your products leave the supplier's country. There shouldn’t be any surprises when your products reach customs. You can ask your supplier ahead of time if they are including the import taxes on your shipping costs. Being completely upfront with your supplier is your best option to make sure that you are not surprised later on.
If you are outside the United States then there is a chance that you are paying an import tax when your products reach your countries customs. So you are not surprised after your products are shipped use duty calculators like this one to figure out how much you might need to pay. You will be notified and given a bill when your products are delivered to your house if there is a duty that needs to be paid.