The mistakes that cost the most, and when they stop being fixable

3 September 2026

The mistakes people make organising an event are almost always the same ones. What changes is when you notice you have made them: some are fixed with a phone call, others, past a certain date, cannot be fixed at all. That is the difference worth knowing.

Booking the date before the objective

The most common one, and it comes from something reasonable: dates and venues are the first things to run out, so there is pressure to lock them.

The problem is that everything else gets built around that choice. If the objective is not settled when you sign, you end up adapting the event to the space instead of the other way round. An award night for top sellers and an internal convention can have identical numbers and want completely different rooms, timings and atmosphere.

When it becomes irreversible: at the venue contract. After that, changing means losing the deposit.

How to avoid it: write the objective of the event in one sentence before calling any venue. It takes a minute and it changes every decision that follows.

Treating the budget as a final number

A budget is not the figure you check at the end of the project. It is a working tool that gets updated every time a quote is signed.

Treat it as a number to verify later and you find out you have overshot when there is nothing left to do about it. Update it as you go and you notice while there are still lines to decide on, which means you get to choose where to cut instead of having the cut chosen for you.

When it becomes irreversible: once most suppliers are signed. From there the room to move is whatever is left, and it is usually the least important part of the event.

How to avoid it: one document, updated at every signature, holding quoted against spent. It does not need to be sophisticated. It needs to exist and to be the only one.

Comparing quotes that are not like for like

Three quotes for the same service almost always arrive with different scopes. One includes transport, another does not. One allows two extra hours of staff. One counts hire separately.

Comparing totals without bringing them back to the same scope means choosing more or less at random. And the mistake does not show immediately: it shows during production, when the lines that were never included start arriving.

When it becomes irreversible: at supplier confirmation. Renegotiating afterwards is possible, from a weak position.

How to avoid it: a table with the lines down the left and the suppliers across the top, filled in row by row, asking each of them what the things they left out would cost. It is tedious, and in my experience the ranking changes very often.

Leaving roles implicit

On long days the difference between an event that flows and one that jams is not the quality of the suppliers. It is how clear it is who reports to whom.

"Someone will handle it" at an event means nobody handles it. And the moment you find out is always the worst one: during build-up, with the audience about to arrive.

The same applies to decisions. If half a delivery is missing during set-up, the person who authorises the alternative has to have been identified already. Chasing an approval while guests are arriving is the fastest way to turn a small problem into a visible delay.

When it becomes irreversible: on the day. There is no time to recover.

How to avoid it: before the event, settle who decides what and within what limit. A narrow, clear margin works better than a vague mandate.

Confirming numbers too late

Catering and transport ask for final numbers days in advance, and after that date every change is chargeable. Guest registrations therefore have to close before that deadline, not alongside it.

The mistake is keeping registrations open until the last moment so as not to lose anyone, and then paying for variations across the board.

When it becomes irreversible: at the confirmation date written in the supplier's contract.

How to avoid it: start from the supplier's deadline and work backwards. Registration closes a few days before it, and gets communicated as a real date.

Skipping the reconciliation

The one nobody ever sees, because the event is over and it seems to have gone well.

Without checking the invoices against what was agreed, and without a final cost picture, the next edition starts again from the same rough estimates. The same mistakes get repeated, the same lines get underestimated, and nobody knows why.

When it becomes irreversible: a few weeks later, when the detail has gone and nobody remembers where the time went.

How to avoid it: a debrief done while it is still warm, covering what worked, what can be improved and why. It is the stage almost everyone skips, and it is the one that makes the second year different from the first.

The stages in the right order are in how to organize a corporate event in Italy. On the two most expensive mistakes, budget and quotes, there is how a corporate event budget is built. If you want someone holding the event days, that is on-site coordination.