Customer Z buys product A at company Y. Company Y charges customer Z amount X. Customer pays amount X. Customer Z waits for company Y to send product. Company Y realizes they made a mistake in calculating amount X and wants to change the deal to amount Q.
As a company owner inside the EU, I can tell you that the exact process is that
company Y is supposed to charge the VAT to customer Z and then pay that amount as taxes to state/country P. So whenever I sell you something (like 3D printed Vive DAS adapters for Pimax headset) for like € 10 excluding VAT, I bill you €12,10 including 21% VAT and that is what you pay me. If I charge you € 10,00 the price excluding VAT would be € 10 / 1,21 = € 8,26 and I would have to pay the remaining € 1,74 as taxes. The core of the matter is that the state charges VAT to my company, and I anticipate on it by taking it into account when I calculate my selling prices.
Now, it could very well be the case that in China and/or in TS’s country, the customer is supposed to pay the taxes directly to the state. In that case, Pimax is not at all bound to pay any of the 8,66%, and it would indeed be a nice gesture for them to pay any of it. The part that I do not understand is where they say that they cannot send product A before customer Z pays them 4% extra. If it’s between customer Z and state P, go ahead and send the product. If it’s between company Y and state P, company Y pays the taxes to state P and may or may not decide to charge customer Z for it - beforehand.
There is one more issue to address: VAT and import taxes are two totally different things. I charge my local customers VAT, or Value Added Taxes, just as my customers in other countries. Import taxes (or import tariffs, rather) may or may not be charged if a product or service leaves one country and enters another. It all depends on trade agreements between the countries involved.
Could it be the case here that this is not VAT at all, and we are seeing dear Mr. President Trump’s famous import taxes against China at work?
TL;DR
If the tax/tariffs are charged to the customer, Pimax is not held to pay any part of it, and they should send the headset because the customer will pay directly to the state. If the tax/tariffs are charged to Pimax, they can’t just decide to have the customer pay for it after the agreement was made.