How much you can charge
No verified state cap. No state cap. The binding limits are the card networks: Visa caps a credit card surcharge at the lower of your merchant discount rate or 3% (reduced from 4% effective 15 April 2023) and Mastercard caps it at 4%. Surcharging debit cards is prohibited nationwide.
Disclosure requirements
Online sellers should surface the surcharge on the first page that mentions credit card payment, not only at the final total, and itemise the amount on the receipt.
Sources
This page is a research summary for merchants, not legal advice, and no attorney-client relationship is created by reading it. Surcharge rules change, they interact with card-network rules and federal law, and they can turn on facts specific to your business. Consult licensed counsel in Michigan before you implement or change a surcharge.
Putting this into practice on Shopify
Rules like these only help if your checkout can actually enforce them, including on Shop Pay, Apple Pay and Google Pay.