Is credit card surcharging legal in Tennessee?

Usually yes, with conditions. Tennessee allows a credit card surcharge but attaches rules you have to meet. Tennessee has no surcharge ban, but the Attorney General has warned that a merchant who fails to disclose, clearly and prominently and before the consumer pays, what it will charge including any additional fees may violate Tennessee law against deceptive or false advertising. The Attorney General also cautions against disguising a surcharge as "cash discounting" and against surcharges above a merchant's typical actual cost. The constraint here is consumer-protection enforcement rather than a surcharge statute.