Refunds and cancellations when only part of the price has been paid
A cancellation mid-schedule is two jobs: stop the dates that have not happened, then work out what of the money already in your hands goes back.
A cancellation mid-schedule is two jobs, not one
When the whole price was taken up front, a cancellation is a single decision: how much goes back. When it was taken across four or six dates, it is two decisions on two different clocks. The first is stopping the payments that have not happened. The second is working out what of the money already in your hands belongs to the customer. The order matters, because the second job is the slow one, and every day it takes can collect another payment you will then have to send back.
So cancel the remaining dates the day you hear, before you have agreed a figure and before you have even replied. A payment that lands after someone has told you in writing that they are cancelling is the fastest way to turn a workable conversation into a dispute with their bank, and leaves you nothing to say. If you want a week to do the sums, or you are hoping to talk them round, pause the schedule and keep the conversation open: a pause can be undone in a minute, a charge taken in the gap cannot be unsent.
Three sums, kept apart
The arithmetic is only hard when the figures get mixed. On the day the request arrives, write down four things:
What you have actually collected — payments that cleared, not payments that were scheduled.
What you have already committed on their behalf and cannot recover: a caterer's deposit, hire ordered, a per-head cost paid on, staff too late to release.
What is still scheduled, with its dates, so you can tell them plainly that none of it will be taken.
How many days sit between today and the date they booked, because that is what your terms turn on.
The refund is the first figure minus the second. It is never below zero and never above the first, and that second limit is the one worth saying out loud: your terms may entitle you to keep more than this customer has paid so far, and when they do, what you are holding is an unpaid balance to invoice, not a refund to work out. Decide in advance whether you will chase it. Plenty of organisers quietly will not, which is a fine answer as long as it was decided rather than discovered.
Write the policy as a staircase, measured from the booked date
One sentence cannot carry this. When everything arrived up front, a non-refundable deposit answered every case. When it arrives across a schedule, the amount in your hands depends on when someone walks away, so the policy has to become a short staircase: up to this many days before the date, everything but the first payment comes back; inside this window, half; inside the last window, nothing more comes back and nothing more is taken. Three steps is usually enough.
Measure every step from the date they booked, never from where they have got to in their plan. Two people can cancel on the same morning having paid very different amounts, because one booked earlier. Pinned to the event, both get the same answer and you can read it off a calendar while they are on the phone. Pinned to the plan, it quietly rewards whoever booked latest.
Send it back the way it came
Refund against the original payments rather than sending a bank transfer. The customer's statement then shows reversals sitting beside the charges, same amounts, same name, which is easier for them to recognise and is the only account of events their bank can follow months later. It also saves you asking a cancelling customer for their bank details. Offer the alternatives before the refund, too: moving the plan to another date, or transferring the booking to someone else, usually costs you less and is often what the customer actually wanted. Say beforehand what travels with a transfer — the payments made so far, the remaining dates, or both — and expect, sooner or later, the refund that is real money leaving your account long after it arrived.
When the cancellation is yours, because you cannot run the thing or the date has moved, everything goes back including the parts your terms call non-refundable, without being asked, and the schedule stops that same day. Either way, keep the note with the plan rather than in a mailbox: the day the request arrived, who stopped the dates, the figure, and how you reached it. Then put the staircase on the page where the customer agrees to those dates in the first place. Nobody reads a cancellation policy at the beginning and everybody reads it at the end, when the only thing that matters is that it still says what it said then.