When should you send an appointment reminder?

Send it while the slot can still be rebooked

The best time to send an appointment reminder is not a fixed number of hours before the appointment. Send it early enough that the customer's answer arrives while you can still give the slot to someone else.

The reminder that matters most asks for an answer: Confirm, Change the time or Cancel. This guide calls it the main reminder. When a customer changes the time or cancels, their slot becomes a freed slot.

So work back from the appointment. First find the decision point: the last moment you can still count on rebooking a freed slot. Then send the main reminder early enough that customers can answer, and those who do not can get a call, by the decision point.

The common default, one reminder the day before, usually fails this test. It still tells you who will not come, but the answers arrive after the decision point, so most freed slots stay empty.

In one line: send the main reminder at the decision point minus the time you give customers to answer, or when the customer must start preparing, whichever is earlier.

Every timing and number in this guide is an example to adapt. None of it is DRING data or industry data.

How many days before the appointment should it go out?

In the example timings below, the main reminder goes out two to five days before the appointment. The number comes from your rebooking time plus the time you give customers to answer, or from the customer's prep time if that is longer.

The rule uses three durations, each set by appointment type:

• Rebooking time: how long before the appointment you need to know that a slot is free, to give it to someone else. That can be a customer from your waitlist (customers who asked for an earlier slot), or another booking you move earlier.
• Wait window: the customer's time to reply, between the main reminder and the follow-up call. A follow-up call goes to customers who did not answer the main reminder within the wait window.
• Prep time: how long before the appointment the customer must start doing something: collect documents, arrange transport, invite colleagues, or make sure someone is home.

The rule, in two lines:

• Decision point = appointment time minus rebooking time.
• Main reminder = decision point minus wait window, or the start of prep time, whichever is earlier.

The table below shows six appointment types. Its values are examples to adapt, not rules, and the wait window is one day in every row.

Each row follows the rule. For the dental check-up, 2 days of rebooking time plus 1 day of wait window gives 3 days. The car service also gives 3 days. Its prep time starts later, so it does not change the main reminder. For the appointment that needs documents, 2 plus 1 gives 3 days. But collecting the documents takes 5 days, so the main reminder goes out 5 days before.

The Short note column says when confirmed customers get a short note. That is a brief message close to the appointment, usually the day before, with practical details: the time, the address and what to bring. No reply is needed.

Clinics have more to settle than timing. Our guide to a clinic reminder flow covers appointment states, channel choice and clinical questions.

What does the schedule look like for one appointment?

For an appointment at 14:00, with a rebooking time of 48 hours and a wait window of 24 hours, the main reminder goes out 3 days before at 10:00. The decision point falls 2 days before at 14:00. Example, not real data.

• 3 days before, 10:00: main reminder, asking for an answer. 76 hours before the appointment.
• 2 days before, 10:00: follow-up call to customers who have not answered, at the end of the 24-hour wait window. 52 hours before.
• 2 days before, 14:00: decision point. 48 hours before. Every freed slot known by now is offered to the waitlist.
• Day before, 16:00: short note to confirmed customers. 22 hours before.
• Appointment day, 14:00: the appointment.

The rule alone gives 72 hours before the appointment: 3 days before at 14:00. This schedule sends the main reminder four hours earlier, at 10:00, so customers can answer during the working day and the follow-up call comes four hours before the decision point. The next section calls this schedule Worked back.

Is the day before too late?

Usually, yes, if you need a day or more to rebook a slot. A reminder the day before still tells you who will not come, but the answers arrive after the decision point, when most freed slots can no longer be rebooked.

Example, not real data: a business has 200 appointments a week and a rebooking time of 48 hours. Times are for an appointment at 14:00.

In both schedules below, the same 30 customers cannot come. Of these, 21 say so in reply to the main reminder, and 6 more on the follow-up call. The other 3 never reply and do not come (21 + 6 + 3 = 30).

A rebooked slot is a freed slot given to another customer. An empty slot is a slot nobody uses: a freed slot that was not rebooked, or the slot of a customer who never replied and did not come.

• Day before: the main reminder goes out the day before at 10:00, and the follow-up call at 15:00, after a wait window of five hours. All 27 answers arrive by about 16:00, 22 hours before the appointment and after the decision point. Few customers on the waitlist can come at such short notice, so only 4 of the 27 freed slots are rebooked. Empty slots: 23 not rebooked + 3 with no reply = 26.
• Worked back: the same message and call, moved earlier. The main reminder goes out 3 days before at 10:00, and the follow-up call 2 days before at 10:00. All 27 answers arrive before the decision point, and 18 of the 27 freed slots are rebooked, about 2 in 3. Empty slots: 9 not rebooked + 3 with no reply = 12.

Same customers, same message and call, same 27 answers. Moving both before the decision point turns 4 rebooked slots into 18, and 26 empty slots into 12. The difference is the timing, not the number of reminders.

The short note in the Worked back schedule does not change these numbers. It helps a customer who confirmed three days before the appointment to remember it.

What if the customer does not reply?

They get a follow-up call when the wait window ends. The call goes only to customers who have not answered the main reminder, and only inside your calling windows, the hours in which you call customers.

Quiet hours and do-not-call flags apply as for any other call. For these rules, see our guide on when to call again and when to stop. In the example schedule, the call goes out 2 days before at 10:00. It can sound like this:

• Agent: "Hello, this is the AI assistant of [business], calling about your appointment on [date] at [time]. Can you still come?"
• Customer: "Ah, no, I can't come that day after all."
• Agent: "No problem. Would you like a new time, or should I cancel it?"
• Customer: "A new time, later that week if possible."
• Agent: "I can offer [new date] at [new time]. Shall I book it?"
• Customer: "Yes, that works."
• Agent: "Done: [new date] at [new time]. Your old time is free now."
• Customer: "Great, thank you. Bye."
• Agent: "Thank you. Goodbye."

The old time is now a freed slot, known before the decision point and in time to offer it to the waitlist.

If the call does not reach the customer either, the booking stands, and your team knows which slots are still unconfirmed. Write every answer, by message or by call, to the same booking record. Our guide to keeping voice and WhatsApp in one record explains why.

Won't customers forget a reminder sent days early?

They might, and that is the job of the short note. Close to the appointment, usually the day before, confirmed customers get the time, the address and what to bring, with no reply needed.

The short note does not ask for an answer again. The answer came earlier, while it was still useful.

Isn't that too many messages?

No. A confirmed customer gets two reminder messages at most: the main reminder and the short note. The follow-up call goes only to customers who did not answer the main reminder.

What if customers book at short notice?

If a customer books after the moment the main reminder would have gone out, for example inside the rebooking time, skip the main reminder. There is no earlier moment to use. Instead, send the booking confirmation, the message sent right after the booking, with the same options: Confirm, Change the time, Cancel.

What time should it arrive, and what should it say?

Send the main reminder at an hour when customers can act and your team can rebook the same day, for example 10:00 on a working day. Keep it short: who you are, the appointment, and three reply options.

A reminder sent late in the evening is often answered only the next morning, which uses up part of the wait window. With a 10:00 main reminder and a 24-hour wait window, the follow-up call also falls at 10:00.

Example wording:

• Main reminder: "Hello [name], this is [business]. Your [service] is on [date] at [time]. Reply 1 to confirm, 2 to change the time, 3 to cancel."
• Short note: "Hello [name], this is [business]. See you tomorrow at [time] at [address]. Please bring [item]. No need to reply."

Give each option one number, so the customer can reply with a single digit. With the main reminder worked back, a reply of 2 or 3 frees a slot before the decision point. Offer new times to a customer who replies 2, and offer the freed slot to the waitlist.

Where does DRING come in?

On DRING, appointment reminders run on Notif, where an appointment reminder confirms or reschedules a booking before the customer misses it. The timing stays yours: your rules set the reminder date for each appointment type, and your system fires the reminder event at that moment.

In the example schedule, the event fires 3 days before at 10:00. Notif then sends the message at once on WhatsApp, SMS or email, chosen per event type, and waits for the wait window you set per event type.

A reply closes the notification, and no call is placed. If the message is still unread when the wait window ends, or read but not answered, an AI agent places the follow-up call. The call already knows what the message said, so the customer does not start over.

The call respects your calling windows, do-not-call flags and consent. The outcome is written back: delivered, read, replied, or called and confirmed. It reaches your CRM like any other call outcome. When your reminder date is worked back from the decision point, the outcome arrives in time for your team to offer the freed slot to the waitlist.

Confirmed connections include, for example, Google Calendar and mainstream CRMs. The exact scope is confirmed during onboarding.

Every DRING agent runs 1,000 to 10,000 simulated conversations, built for your company, before the first real call.

To try this on your own bookings, request a callback. Bring one appointment type, with its rebooking time and the time your reminder goes out today, and we will walk through the message, the wait window and the call.