You'll get hit with tariffs and they'll hold your merchandise until you pay. I ordered some things from the UK a year ago and was very careful to keep my total under the $200 threshold which seemed to be the amount over which you had to pay a tariff. The problem was the company didn't itemize the shipping form and the shipping and handling fee was added on to the value of the merchandise, and hence, I had to pay a tariff when I hadn't before. I complained to the company. I think they now have a notice on their website about this. The whole process made me very wary of buying things from overseas, as the tariff assessment seems to be rather random.
Back in the early ‘80s my wife and I toured Europe and my wife bought some crystal items to bring home. A couple of weeks after we got home we started getting letters and even a phone call from the shop where she bought the crystal. Apparently, they had forgotten to collect the VAT. Since we never heard of a “VAT” and couldn’t get an understandable explanation of what it was for from the guy who called us, we just laughed it off.