Hi @essentialnails.  There is no mechanism, outside of online booking or online store sales, that Square  has for collecting and storing customer card information.  To answer your questions above, I would never recommend using text or email to collect sensitive customer information like this.  There is just too much that can go wrong, especially on the customers’ end of things.  Text and Email just aren’t that secure.

Having said that, I can recommend something.  There is an app/service called Jotform.  It has full SSL security built into the forms that you create with it.  You can use it to collect information which will be securely stored for you.  It will notify you when a customer submits information which you can then put into their Square customer record.  Basically, you would create a form for the customer to fill out.  Send them a link to your form (via text or email is safe since the customer would use their interface which is SSL compliant).

Regards,