Hola Annel. We run shopify based shopidonea.com in Mexico. The easiest way is to let your customers know ( en preguntas frequentes o terminos y condiciones) that if they want an official invoice (deducible ante SAT) they should contact you with all their invoicing info (rfc etc.) so you can send them your invoice (That is if you have a registered company). Also be sure to let them know that you can only invoice within the same month you delivered the product. (otherwise you have a problem) Hope this helped. Un saludo
