Do restaurants HAVE to give you a physical receipt? (Credit Card)?

[I want to be 165 xD]

I'm trying to save some money for my restaurant by moving to Square, a credit card machine company. It allows me to charge customers' credit card on my iPhone but thing is, it only allows me to give out SMS receipts or E-mail. How can I give customers who don't have email nor sms? (like older people)? Do we have to give them a receipt? Can I just write a receipt for the credit card amount?
First of all, I will be giving them the receipts via SMS or E-mail for those that have it or don't mind receiving it via electronically. However, if people prefer a PRINTED receipt, I was thinking "why not write them a receipt of how much they paid in card and put mine AND their signature on it." You know those Receipts that they sell in Office Depot that have 2 layers of white and yellow papers? Wouldn't that work?

 

[kimbershoemaker]

Finally, an issue that I am passionate about. I have looked for information of this forum for the last several hours. Your posting is greatly appreciated.