A missed appointment costs a slot, a prepped vehicle and a place in an already tight schedule. The trade calls it a no-show, and more statistics circulate about it than evidence. The only field that measures the phenomenon properly is medicine. A systematic review and meta-analysis of twelve studies (Cochrane CENTRAL, MEDLINE, Embase and PubMed databases) finds that SMS reminders bring the risk of non-attendance down to a relative risk of 0.77, with a 95 % confidence interval of 0.71 to 0.84. Close to a quarter less risk. That figure is medical, and it does not become automotive because someone copies it into an automotive article. The mechanism, on the other hand, travels: a reminder sent at the right moment brings back people who would otherwise not have shown up.

Three levers follow, and they do not carry the same weight. Sending a reminder: proven. Wording it concretely: proven, and free. Qualifying the buyer before booking the slot: sensible, coherent, never measured. An honest piece of writing keeps the three apart.

Nobody measures automotive no-shows seriously

The most widely repeated figure in the trade, an average show rate somewhere between 50 and 60 %, comes from a BDC software vendor. No published methodology, no panel, no measurement period. It has been copied for years by sites that all sell, in one form or another, the solution to the problem they describe. Osmosia will not quote it.

One source stands out for its transparency. Foureyes, an automotive sales software vendor, publishes its methodology and its panel: around 700 US dealerships across the second half of 2023. Its April 2025 data show that 78 % of phone leads turn into a booked appointment on used vehicles, against 44 % of internet leads. Two caveats apply, and they are rarely stated. These are appointment set rates, not show rates: they say how many contacts accept a slot, not how many turn up. And they are US figures, from a market whose distribution structure looks nothing like ours. Foureyes numbers travel with the label “according to Foureyes, an automotive sales software vendor”, never without it.

That documentary vacuum has a practical consequence. An independent used car dealer who wants to manage no-shows has no reliable external benchmark. Only his own: slots booked, slots honoured, month after month. No benchmark will replace that count.

The only solid evidence comes from medicine

In healthcare, the subject is covered by randomised controlled trials and meta-analyses. That is where the evidence sits, and saying so is part of the argument.

A meta-analysis of ten randomised trials published on 6 March 2026 in the Journal of Hospital Management and Health Policy measures an 11 % increase in attendance at outpatient hospital appointments thanks to reminders (relative risk 1.11, 95 % confidence interval 1.05 to 1.19). The benefit holds for SMS reminders and for phone calls alike. The authors flag strong heterogeneity across trials.

One question every professional asks: is a phone call not better than a text? Geneva University Hospitals asked exactly that in a randomised non-inferiority trial run on 6,450 patients between November 2010 and April 2011. SMS reminder or phone reminder, twenty-four hours before the consultation. Missed appointment rates: 11.7 % for SMS, 10.2 % for the call, with no statistically significant difference (p = 0.07). Only SMS reminders were cost-effective. No patient reported discomfort, and three quarters of those surveyed recommended rolling the system out permanently.

Translated for a dealer selling a hundred cars a year: the written message does the work of the call, for a fraction of the time, and irritates no one.

Wording changes the outcome, at zero cost

This is the most underused finding in the file, and the most directly actionable.

Hallsworth, Berry, Sanders and their co-authors ran two randomised trials in the United Kingdom, one on 10,111 participants between November 2013 and January 2014, the other on 9,848 participants between March and May 2014. Four reminder wordings, sent five days before the appointment. The message stating the concrete cost of a missed appointment to the health system produced a non-attendance rate of 8.4 %, against 11.1 % for the existing message (odds ratio 0.74, 95 % confidence interval 0.61 to 0.89, p < 0.01). The second trial replicated the effect and added a decisive detail: expressing the same idea in general terms was significantly less effective, at 9.9 %. The authors estimate that switching to the specific message would have prevented 5,800 missed appointments a year in the trust concerned. Cost of the operation: nothing. They acknowledge two limits, a single English site and usable phone records for one in five eligible patients.

Concrete beats general. A reminder saying “your appointment is confirmed at 3 pm” works less well than one saying “the grey Clio III is prepped and ready for your test drive at 3 pm, Julien will meet you at 12 rue des Ateliers”. The vehicle, the time, the person, the address. A vague appointment inflates the number of slots booked and destroys the number of slots honoured.

One variation circulates in sales training: invoking the scarcity of the vehicle to create pressure to attend. It is only usable if it is true. Telling a buyer that others are viewing the car when nobody asked is a misleading commercial practice.

Two channels beat one

A randomised trial in outpatient paediatrics, run on 170 patients between August 2014 and February 2015, tested adding an SMS to a voice reminder received by everyone. The missed appointment rate fell to 23.5 % in the group receiving both messages, against 38.1 % in the group receiving only one, a gap of 14.6 points (p = 0.04).

Redundancy is not harassment. A buyer who exchanged messages on a classifieds platform does not necessarily open that inbox on the morning of the appointment. He checks his texts. The reverse holds too. Doubling the channel raises the odds that the message is read while it can still change something.

Qualify before booking: a sound mechanism, not a statistic

No study consulted here shows that a qualified prospect honours his appointment more often. The reasoning stands up, it has not been measured, and it will not be presented here as data.

What can be asserted belongs to the arithmetic of time. A slot blocked for a contact who never mentioned a budget, a timeframe or an intention to test drive is a slot with low expected value. Osmosia’s scoring ranks exactly those signals: a confirmed appointment with a date and a time weighs heavily, a request for a phone call weighs more than a question about colour, a mention of financing or a down payment is not enough to make a hot prospect. The qualification threshold at which a lead reaches you is a setting you choose, not a constant.

There is a cost you do not see. For an independent used car dealer, margin comes from stock rotation, and immobilised time is immobilised capital. On used electric vehicles, the Mobilians and Avere-France barometer for the fourth quarter of 2025 measures an average resale time of 161 days, all ages combined. Two mornings lost waiting for buyers who never come are not recovered.

And an automotive no-show is not a postponement. Buyers visit few sellers, a used car is a unique item, and the one who does not come to you often buys elsewhere.

Is an appointment reminder commercial prospecting?

No, as long as it sells nothing. The CNIL, the French data protection authority, explicitly distinguishes relational communications from commercial prospecting. Relational communications support the customer within an existing commercial relationship, with no promotional purpose: order confirmations, shipping notifications, account alerts. An appointment reminder belongs to that category.

The tipping point is sharp, and the CNIL states it plainly: such messages must not conceal promotional content. A message that highlights an offer or encourages a purchase may be reclassified as commercial prospecting, subject to the prior consent required by article L.34-5 of the French Postal and Electronic Communications Code. The classification does not rest on content alone, but above all on the purpose being pursued.

In practice: “Reminder: your test drive of the Clio III today at 3 pm, 12 rue des Ateliers” is a relational communication. The same message followed by “check out our other vehicles” is not. Separately, the rules on telephone prospecting change on 11 August 2026, according to the CNIL. Before settling a sending policy, have it reviewed by a legal adviser: this section informs, it does not replace a lawyer’s opinion.

What Osmosia does, and what it does not claim

Osmosia answers your leads in under fifteen minutes, seven days a week, from 7 am to 11 pm, inside the classifieds platform inbox. It scores every conversation, escalates only the leads that cross your threshold, offers a precise slot and books the appointment. On the day of the appointment, it sends a reminder, by SMS and in the listing inbox.

The reminder goes out on the day itself. That is a product decision, not a scientifically validated optimum: the trials cited test twenty-four hour and five day lead times, and none demonstrates that same-day is superior. The choice defends itself on proximity to the decision, at the moment the buyer plans his day.

Osmosia does not promise you a percentage of no-shows removed. That figure does not exist, nobody has measured it seriously in the car trade, and inventing it would cost more than writing it could ever earn. What it does: send the reminder every time, word it with the vehicle, the time, the place and the person, across two channels. The three mechanisms research documents.