A number of states suspend sales tax on selected goods for a few days each year. The exemptions are narrower than the advertising suggests, and their main effect is on when people buy.
The exemption is written item by item
Each holiday is created by state legislation that lists qualifying categories, and the lists are specific enough to draw odd lines between similar products.
Clothing may qualify while accessories do not, or a computer may qualify while a peripheral sold separately does not. Retailers receive a state-issued guide describing exactly which items are covered.
Because the definitions come from statute rather than from retail categories, staff at the register frequently rely on that guide to answer questions the store's own product hierarchy cannot resolve.
Price caps limit the benefit per item
Most holidays exempt an item only up to a stated price, above which the entire item becomes taxable rather than just the excess.
That cliff means a purchase priced slightly over the cap costs noticeably more than one priced just under, which pushes retailers to set prices below the threshold during the period.
Caps also mean the benefit is concentrated on mid-priced goods. Inexpensive items save very little, and expensive ones fall outside the exemption entirely.
Local taxes may or may not follow
Sales tax in most states combines a state rate with county, city and district rates, and a holiday enacted at state level does not automatically suspend the local portion.
Some states require localities to participate, others allow them to opt out, and the result is that the same purchase saves different amounts in different towns.
Online orders follow destination-based sourcing rules in most states, so eligibility is determined by the shipping address rather than by where the seller is located.
Timing shifts rather than new spending
Economists studying these holidays generally find that households move planned purchases into the exempt window instead of buying substantially more overall.
Retailers respond by scheduling promotions around the dates, which compounds the effect and makes the weekend look busier than the underlying demand would suggest.
The weeks immediately before and after tend to run correspondingly quiet, a pattern store managers plan staffing around each year.
Administration costs fall on retailers
Systems must be reprogrammed to suspend tax on qualifying items for a defined period, then reprogrammed again afterward, with the burden falling hardest on small independent stores.
Errors in either direction create problems, since undercollected tax is still owed to the state and overcollected tax has to be refunded or remitted.
Because rules are rewritten from year to year, retailers treat each holiday as a fresh implementation rather than as a setting that stays configured.