The proposed American-imposed tariffs on goods imported into the US work, as best I understand matters, by obliging the person or company importing something across the US border to pay the tariff as an import tax.
The UK does it this way and has for as long as I can remember. I recall importing a carpet from India a long time ago and having it held at Tilbury until I paid the duty, at which point it was released for delivery.
Oddly, buying into the UK from America with eBay required eBay to collect VAT (the Value Added Tax paid on many goods at the time of purchase within the UK itself) prior to despatch. That isn't a tariff, it's the VAT imposed at the border crossing. I only mention it to distinguish it from tariffs which are different.
As and when I notice a tariff rate being imposed or changed I'll note it here. I think https://hts.usitc.gov/ is the relevant bible in this regard - "The Harmonized Tariff Schedule of the United States (HTS) sets out the tariff rates and statistical categories for all merchandise imported into the United States".
The help system shows what the three "rate" columns mean:
The final three columns appear together under a superior column titled “Rates of Duty.” Rates of duty for the subheadings are in column 1-general, column 1-special, and column 2.
Column 1- general identifies the rates for countries that have trade agreements, generally under the World Trade Organization, or are entitled to most favored nation treatment, known in the United States as normal trade relations (NTR) status. Almost all countries of the world are eligible to receive these duty rates.
Countries being given column 1-special duty rates must all be eligible for general or NTR duty rates. Column 1- special identifies lower-than-general or duty-free rates for products under free trade agreements (such as USMCA), preference programs (such as GSP), or statutes. Beside the special rate is a list of all programs eligible for that rate when the items meet particular criteria listed in general notes and when the importer claims it for each shipment. When an importer fails to claim a special duty rate, or where no special rate of duty is provided for a subheading, the rate of duty in column 1- general applies.
Rates of duty in column 2 apply to products of countries listed in HTS general note 3(b)—at the time this document was posted these countries are: Belarus, Cuba, North Korea, and Russia.
https://www.usitc.gov/harmonized_tariff ... _questions