Why Checkout Totals Surprise You Even When You Knew About the Tax

You know the tag on the shelf isn’t the whole price. Sales tax gets added at the register, a service fee appears on the last screen of a ticket site, and none of it is news to you. So when the total comes out higher than you expected, it feels like a lapse in mental arithmetic, not a flaw in how you decide. You looked at the price. You knew the rest was coming.

A grocery store in Northern California once moved the sales tax onto its shelf tags. StubHub, the ticket resale site, tested moving its fees from the last screen to the first. Side by side, the two tests answer a narrow question. Why does a cost you already know about keep catching you at checkout, and what habit lets you judge a purchase by the number you will actually pay?

Tags with the tax already on them

The grocery test was run in 2006 by the economists Chetty, Looney and Kroft. For three weeks, they posted tax-inclusive prices on 750 products normally subject to sales tax. A shopper reaching for one of those items saw the amount they would pay at the register, instead of the pre-tax figure American shelf tags usually show.

The tag changed; the tax owed did not. The researchers then used scanner data to compare sales of those products with control products and control stores that kept the usual tags. Demand for the treated products fell by 8 percent. That number describes what went through the checkouts of one store over three weeks, measured against the controls. It shows that the same tax, shown at the shelf, changed what people bought there. It cannot show what any single shopper was thinking.

Those shoppers would have paid exactly the same tax at the register either way. Seeing it on the shelf, while they were still choosing, was enough to take 8 percent off demand.

So did those shoppers simply not know about the tax? The paper also reports that surveyed shoppers mostly knew which items were taxed, which would mean the new tags added little they hadn’t already been told.

The same paper looked at alcohol from a different angle, using past changes in state taxes rather than an experiment. Increases in alcohol excise taxes, which are built into the posted price, reduced alcohol consumption significantly more than increases in sales taxes, which are added at the register. Because that analysis is observational, it points the same way without proving cause by itself.

A ticket site that put the fees up front

Unlike the alcohol comparison, the StubHub study was a field experiment. Blake, Moshary, Sweeney and Tadelis analyzed it on the ticket resale site, where some buyers saw the full price, fees included, from the start. Others saw the fees only when they reached checkout.

When the full price was visible from the start, buyers purchased fewer tickets and chose lower-quality ones. The shift toward lower-quality tickets accounted for at least 28% of the overall drop in revenue. A visible full price did more than stop some sales. It changed which seats people judged to be worth it.

Would regular users see through the late fees? The effects lasted beyond a first purchase, and they also appeared among experienced users of the site.

The order of the numbers

Put the two scenes side by side and what they share is the order of events. In the grocery store, the tax normally arrived at the register. On StubHub, the fee normally arrived at checkout. In both, moving that extra cost into the first number people saw changed what they chose, though the cost itself was no bigger.

A third study puts a size on the discount. Taubinsky and Rees-Jones ran an online shopping experiment with 2,998 people buying household products. On average, those shoppers responded to existing sales taxes as if the taxes were about a quarter of their real size. The study measured that underreaction, not its cause. It does fit the two scenes, though: a cost that sits outside the number being compared gets only part of its weight.

One thing to try

Some shoppers get this habit handed to them. UK guidance for traders says that “all price indications that can be seen by consumers must include VAT and any other compulsory charges or taxes.” Delivery may be listed separately if that is made clear. A British shelf tag, then, puts close to the full price where the choice is made. Where the tag doesn’t, you can, at one moment: right before you commit.

In the US, two kinds of site now do part of this for you. Since May 12, 2025, the FTC’s Rule on Unfair or Deceptive Fees has required sellers of live-event tickets and short-term lodging to show the total price, fees included, up front. The habit matters most outside those two categories, at any online checkout where a service, booking or handling charge first appears on the last screen. There, go all the way to the final payment screen before settling on anything. Read the total with every fee and tax in it. Then go back to the product page with that total in mind and choose again. If you land on the same choice, buy it. If you change your mind, the first number was doing more of the deciding than it seemed.

In a US store, keep the habit for the larger items rather than every can of soup. Before something expensive goes into the cart, add your local sales tax to the tag, on your phone if needed, and ask whether you would still pick it at that amount. You may well buy it anyway. The difference is that the number on the receipt is the one that made the call.

Where this breaks down

The discount is not the same for everyone. In the Taubinsky and Rees-Jones experiment, the quarter-size response was an average, and individuals differed substantially. Attention also rose with the tax rate. The average should not be applied to every person or every size of cost.

That leaves room for a sensible shortcut. On a small, routine purchase, ignoring a few percent costs little. Is doing the sum every time worth the effort? Often it isn’t. The gap matters most on big or repeated spending.

The grocery result covers one store and a few product categories, and the StubHub test covered event tickets on one platform. None of these studies shows whether the effect would last if full-price tags became permanent. Shoppers might adjust once the tags stopped being new, or they might not; the studies don’t say.

The FTC rule that now covers tickets and lodging does not cap what those fees can be, and it does nothing to put sales tax on American shelf tags.

So the checkout total keeps surprising you for a reason that has little to do with what you know. You chose on the tag, and the tax or fee arrived after the choice was made, carrying only part of its weight. Reading the final screen before you pick moves that cost back to where the grocery-store tags put it: in front of you while you are still deciding.