This same scenario has happened to me before and I recall being uncomfortable about it as well. Carol Wight of the New Mexico Restaurant Association says she doesn't think she's ever encountered the problem but had an idea as to why it happens. “It could be that they don't have a credit card machine that allows them to put tips on afterwards or it doesn't have a space for tips.” Normally, at the end of the shift, a server or manager will take all the credit card receipts and re-run them through the machine, adding the tip amounts in. “Some older machines don't have the capacity to do that,” Wight said.
But Terri Bussey of Southwest Transaction Services, a local company that handles credit card processing services, said that while it was true some older machines couldn't handle re-running tips, most of those were the same machines that produced receipts showing the purchaser's whole credit card number. It is now illegal to give a receipt that reveals an entire account number, she said, so those machines shouldn't be in use anymore. Newer machines do have the capability to accept tips at the time of processing, but she said it would be the restaurant's decision to do it that way and she couldn't see why they would.
Representatives from a handful of restaurants we called said they had no idea why a patron would be verbally asked for a tip amount. The only thing I could come up with was simple: saving time. It's possible that a server might ask for the tip amount up front so that the card wouldn't have to be re-run later.
If this happens to you and you're uncomfortable about it, we recommend asking your server if you can simply write the tip amount on the receipt. If he balks, don't be afraid to ask why. This is a relatively uncommon way of doing things and he should be surprised that you're uncomfortable with it.
The two-run system has another flaw in addition to taking extra time. According to Wight, Visa and Mastercard will withhold 20 percent of your total charge at a restaurant for up to 24 hours, reserving enough to cover your tip. In theory that amount should be released as soon as the tip is run through again but the Restaurant Association has had several calls complaining about the procedure, she said. “It's something Visa and Mastercard are doing, not the restaurants,” she insisted. In the meantime, this withholding could potentially affect your available balance or throw off your checkbook balancing efforts.