When your numbers don't match the supplier's numbers.

There's a particular feeling — you'll know it — when you're on the phone with a hotel the day before arrival and their room count is different from yours. Not massively different. Maybe two rooms. But different. And you can't immediately tell who's right, because your number came from a spreadsheet you updated last Thursday, and theirs came from a confirmation email you sent, which was based on a version of that spreadsheet from the week before.

Both numbers feel real. That's what makes it horrible.

We spent twenty minutes on one call like that working backwards through two weeks of emails before we found it — a late booking that had gone into the system but hadn't made it onto the rooming list. Two rooms. An easy fix. But the thirty seconds of cold panic at the start of the call had already happened.

Every events business I've worked with — including my own for most of two decades — runs some version of the same thing: a way of taking bookings, a spreadsheet or document that translates those bookings into something suppliers can act on, and a person who copies between them. The copying usually happens in a gap during the day, or at the end of it, and it's usually done by someone who already has seventeen other things on.

That join isn't technical. It's a person, tired, selecting cells and pasting. And unlike a piece of code, it doesn't throw an error when it goes wrong. It just produces a number that looks exactly like a correct number, and sends it somewhere.

It's rarely one catastrophic mistake. It's a confirmation sent before the last three bookings came in. It's a row that didn't paste cleanly and got read as a different room type. It's a total that was right when you wrote it and wrong by the time it reached the supplier, because someone booked in the window between the two.

We had a run of events once where rooming lists were going to two different contacts at the same hotel — the conference coordinator and the rooms coordinator — and they weren't fully comparing notes with each other. Our numbers looked fine from our side. From their side, nobody had the complete picture. It took a check-in problem to surface it.

The other thing that bites you is versions. An attachment is always a snapshot. Send a rooming list on Monday, someone books on Tuesday, and the file the hotel has is already wrong. Most of the time this gets caught. Sometimes it doesn't, and you find out at eight in the morning.

The fix isn't always a new system — though sometimes it is. Before you spend money on software, it's worth working out where your joins actually are. The places where information moves from one tool to another by human hand, usually under time pressure.

The rooming list emailed as an attachment: what if it's last week's version? The supplier confirmation that comes back as a PDF: does anyone check it against your numbers, and when? The allocation you built at ten o'clock at night: does anyone else understand it well enough to spot a mistake before it goes out?

If the answer to most of those is 'I'd catch it', that's probably where your risk is sitting. Not in the tools themselves, but in the handoffs between them.

Getting those right — whether by building something that removes the manual step, or just by putting a check in place — tends to make more difference than almost anything else. If you want to talk through where yours are, get in touch.