Trash this card. Put a Tariff token on top of a Supply pile.
Cards from a Supply pile cost 1 Coin more to buy per Tariff token on that pile.
This card uses a new token type: Tariff tokens. Any home-made token can be used, or in games not using the Embargo card from Seaside, its tokens make a good substitute.
You can pick any pile in the Supply. The cost of the cards in that pile are more only for the purposes of buying them. Gaining the cards by other means is unaffected. Unlike Bridge, the card costs are not affected universally.
The cost will be higher for you too, and will be in effect for this turn's Buy phase.
If multiple Tariff cards are used to put Tariff tokens on the same pile, the cost increase is cumulative +1 Coin per token.
If you Throne Room a Tariff, you place two Tariff tokens and they do not have to go on the same Supply pile.
The supply of Tariff tokens is not intended to be limited. If you run out, use another replacement token to mark affected piles.