Empty appointments: measure which slots you can recover

A cancellation in time lets you reorganise the diary. Having someone else fill that slot is a different result. It is worth recording them separately before attributing income to a reminder system.

I would start with several weeks of diary records: scheduled appointments, absences without notice, advance cancellations and slots ultimately filled. I would record duration too. Ten fifteen-minute appointments and ten one-hour appointments do not leave the same unused capacity.

A reminder may help, but how needs checking

I would not infer from the diary why someone did not attend. There may have been forgetfulness, difficulty giving notice or an unexpected event; your records do not distinguish these causes without more information.

There is evidence that message content can affect attendance. Two randomised trials published in 2015 compared different SMS wordings in an English hospital. Reminders were sent five days beforehand and results varied with the wording. That is a specific context: it does not show how much a WhatsApp message sent 24 hours beforehand would reduce missed appointments in a Spanish business.

I would use it as a reason to test and measure the message, rather than promise a percentage or copy a hospital-cost reference that does not apply to your service.

A simple confirmation workflow

This workflow is hypothetical. The diary generates a reminder with the date, time and a clear way to confirm, cancel or request a change. One possible message is: “A reminder of your appointment on Tuesday at 11:00. You can confirm or cancel through this link. If you need help changing it, reply to this message.”

If the person confirms, the booking is marked confirmed; that does not ensure attendance. If they cancel, the identified booking is updated. An ambiguous response goes to a person. If they do not reply, the appointment remains: silence does not authorise deletion of a booking.

Once a slot is free, the waiting list only helps if people have compatible availability and have requested that notification. Before confirming a new booking, the system rechecks and locks the slot to avoid two appointments at the same time. The chosen channel must support the proposed workflow and comply with its terms; I would not assume that every messaging account supports it.

From an empty slot to margin

Suppose a monthly example, without client data: ten one-hour absences. With reminders, four people give notice in time. Of those four slots, only two are filled with additional appointments that do not displace bookings from another day.

If each service bills €60 and has €15 of variable cost, the hypothetical additional margin is 2 × (60 − 15) = €90. With €40 for tools and messages and one hour of additional administration valued at €25, that leaves 90 − 40 − 25 = €25 a month, before implementation and tax.

The calculation does not turn ten absences into €600 recovered. It depends on two additional appointments delivered and paid for, complete costs and their not being sales you would have made later anyway. If no slot is filled, the diary may be better organised without additional income.

During the trial, I would measure message delivery, confirmations, timely cancellations, absences and additional appointments. I would also review the work of handling responses. There is no universal €200 threshold: your decision depends on recoverable margin and the cost of achieving it.