Would missing HS Codes cause VAT & Custom Duties?

[Dunne-08]

Our products are being held in customs and our customers have to pay VAT/duties on arrival, we have not included any HS Codes on our products. Would that be the cause of the being held and duties being added?

Our store is relatively new and we were unaware of HS codes and what they were so they were not added to products.

[FC-JEE]

Yes , you have sent the products DDU , Delivery Duty Unpaid so local customs will assess items and charger duties and taxes 

if you have the HS Codes and use a service for International Shipping to collect and pay duties and taxes at checkout it would avoid this as you would be shipping DDP . Just having the HS codes in your store will not avoid paying duties and taxes