Why do people post stuff like this? I’m not forcing you to come up with a solution yourself. I’m not forcing you to use this solution. If you don’t feel like contributing there are plenty other threads out there.
I do use paper receipts today. It would be simpler if I could somehow glance down my CC statement and easily notice a modified entry. I’m searching for that system that I view as simpler. You may not view it as simpler and that’s fine, but please keep that opinion to yourself.
Thank you for deliberately cutting out the portion of my response that actually answers the question you asked and then claiming that I’m not contributing to your discussion.
The point, that I and many others have attempted to tell you, is that no system you devise will work as simply or as effectively as keeping your receipts and comparing it to your statements. And I’d think that a person looking to rationally solve a problem would be interested in the most rational solution there is.
How about something that doesn’t require any calculation on the verification end, like taking the digit in the one’s place then the cents are the next two sequential digits? Then back-calculate the tip. When you get your statement you don’t have to calculate a checksum.
Food 32.57
Tip 6.00
Total 38.57
Desired Total 38.90
Revised tip 6.33
FWIW I have used my credit card in restaurants for over 30 years. I enter receipts in Quicken and reconcile my statements (now it’s all electronic and largely automated). Only twice has a credit card amount not matched. Once it was my mistake; I made an arithmetic error in the restaurant when adding up the tip, and the restaurant used the tip amount I had written and corrected the total. The other time the total didn’t match the receipt. The bank just credited me the amount because it was so small, and did not pursue it as fraud.
Your point assumes that you can measure, for a different person, which system is simpler, easier and more effective. But you can’t perform that measurement for a different person through a few posts on a message boards. There are variables involved based on personality, lifestyle, volume of transactions, etc. You are ignoring all of this in your calculation.
Even on the surface, comparing a bunch of credit card transactions on a statement to a bunch of paper transactions is slower than scanning for certain number patterns. Obviously the trade-off is a little more work up front, but for me personally, the up front work would be easier than matching trans to receipts later as long as the up front method was simple (which it can be).
Merchants are required to keep their copies of the receipts in case they are audited by the credit card company or if they need to dispute a chargeback. In the case I referred to above, the restaurant provided a copy of the original receipt that I signed and the bank sent it to me and it was clear I had made an error.
The difference is that, if you just put a thick line in the Tip section, it’s harder to mess with the credit card slip, and easier to prove fraud.
Changing a 3 to an 8, or a 5 to a 6, is relatively easy. But if there’s nothing but a big line there, then writing numbers over it will be much more obvious.
I believe two checksum digits would be required to accomplish this. For instance, you could repeat the ‘ones’ digit in the ‘tenths’ position, and then use the normal checksum of all digits in the ‘hundredths’ position.
Rather than add the numbers directly, add them after multiplying each by a place-dependent mask. If you only want to catch adjacent transpositions, a simple mask will work, such as multiplying alternating digits by 2 before adding them. Example:
Value:
dc.ba
Mask:
12.10
The “0” in the mask just shows that the last digit isn’t involved in the checksum. If you have a $100+ bill, the mask becomes 212.10. $1000+ would use 1212.10 (etc.) So, the sum for a bill becomes: b+2c+d ( +2e + f +2g + …).
A bill: 12.43 + 2.46 = 14.89. We want the last digit to be 1 + 42 + 8 = 7, so we must remove two cents from the tip. This leaves the total at 14.87. A transposition of, say, the 1 and 4 would imply a checksum digit of 4 + 12 + 8 = 4, which would indicate the error, as 4!=7.
Cash is definitely the best solution. If the whole bill is paid in cash, there’s absolutely no opportunity for restaurant employees to key in anything.
Cash also requires the least of the OP’s time, and it saves the restaurant 2% or so in processing fees.
How many restaurants still use this ancient method with CC’s?
Whenever I use a CC in a restaurant the waiter brings the CC machine to the table and I key in the tip. It then prints out the receipt showing the bill, tip and total.
So the restaurant never gets hold of my card and I can see that everything’s correct.
I didn’t mean to call you out specifically. Thank you for the contribution part of your post. You were just one of many posters in this thread who felt the need to post something to the effect of “What you want to do is stupid. Don’t do it at all or do it this other way.” I just don’t understand the point of posting something disparaging like that.
I haven’t seen one of those slide action machines anywhere for what seems like years. CC transactions are so much faster and more efficient now. I’m very surprised the on line machines haven’t made their way into restaurants there.
I don’t believe this will eliminate the problem. I’m pretty sure the server still enters the total by hand. So whether the bill is this:
Food: 23.00
Tip: 4.00
Total: 27.00
or this:
Food: 23.00
Tip: -----
Total: 23.00
It’s still up to the server to enter 27 or 23 into some computer. If someone with eyeballs actually checks receipts against totals entered they will catch mistakes, but typically it seems businesses just spot check or not check at all.
And I’ll clarify as to why, for me, a checksum is simpler than checking receipts. I’ve been checking receipts for a couple of years and the only mistakes I’ve found have been from the editable receipts (tip). Normal stores which don’t allow modifications to the total have never presented a problem. So checking just the modified receipts will catch most (or all) of the errors.
I usually have 20-30 food receipts at the end of the month. It’s a hassle to try to match up each receipt with each entry on the statement. Even if I keep my receipts in order, the transactions on the statement aren’t necessarily in that same order. I often go to the same sets of restaurants. This means have to figure out which of the 5 or so “Moe’s Cafe” receipts goes with which record in the statement.
My credit card company lets me download the statement. I can write a program to auto compute the checksums of the entries and kick out the ones which don’t match. By having a checksum, I can run my program and automatically know if any records look wonky. Then I just look for that single receipt to see if there’s a real problem.
What do you mean by “slide action machines”? Do you mean the ones that are heavy and mechanical and carbon copy? Those I (almost) never see. The standard here is you give them the credit card, they go back and swipe it through their credit card machine (the online kind with the magnetic strip reader), and they come back to you with a receipt that says Subtotal, Tip, and Total. You fill in the tip and total lines, sign the receipt, and leave it at the table when you leave. Oh, and take your credit card back, of course.
edit: So where do you live? I’ve traveled around a good bit, and I can’t recall coming across any restaurants where they brought the card reader to your table. It’s completely possible I’m forgetting, but the last few trips I’ve been to Wisconsin, Indiana, California, New York, Arizona, etc., I cannot remember any place using this method. Is this something more popular outside the US?
UK (although I think this applies throughout Europe).
I didn’t realise that chip and pin had not reached (the whole of) the US.
The system here is that they don’t ever get to take your card. They bring a machine to the table and you insert the card and enter your pin. Then you remove the card and they print the receipt. It’s much safer than letting people wander off with your card.
The system is also a lot more streamlined and faster to use in use in other retail establishments as there is no signing/checking of signatures.