How can I charge a fixed federal excess tax on specific product variants?

Hi there, we sell truck tires that require an additional FET (federal excess tax) on 7 of our sizes (variants). Right now Shopify do not allow for additional taxes with a fixed amount. Does anyone know of a workaround for something like this? We are looking to add it during checkout. We thought of adding it as an additional variant so it is charged but we fear that that is not the correct way to do it.

I know this is old, but I was searching for a similar solution and I found this were you able to find anything to help solve your issues with federal tax?

Hey there, @craig51 ! Thanks for taking the time to reach out to the Shopify Community Forums and for following up on this older thread! My name is Imogen. It’s good to meet you!

I wanted to jump in to suggest taking the time to reach out to our Authenticated Support Team via our Help Center regarding your questions around charing additional taxes on specific goods. This will allow our team to get you authenticated so they can have the ability to access your store and account information. Additionally, this will allow our team to collect some specific information around what it is that you’re trying to accomplish and relay with our Tax Team to see how we’re able to lend a hand and support you.