A customer emails to ask why they got two order confirmations. Or you notice the same order twice in your spreadsheet, two invoices for one sale, or a booking in the calendar twice.

It's usually harmless the first time. But a repeated action can quietly add up: stock counted down twice, a thank-you email sent every time a review is edited, a customer who starts to wonder whether they were charged twice.

This guide is a check you can do yourself in about ten minutes. You don't change anything. You only look.

Why automations repeat themselves

An automation does its job once for every time it starts. When something happens twice, it's almost always because it started twice. These are the common reasons:

  • Two automations doing one job. A new automation was built and the old one was never switched off. Or your shop already sends its own confirmation email, and an automation sends another.
  • The automation starts again when something is edited. Some automations start on new or updated records. In Zapier, for example, the Google Sheets trigger called "New or Updated Spreadsheet Row" can start again every time a row is changed. Correct a typo, and it counts as a fresh start.
  • A run was repeated after a problem. Some ways of running something again start from the very beginning, so steps that already worked happen a second time. And a step that seemed to fail, because the other app was slow to answer, may in fact have worked, so trying it again does it twice.
  • The customer pressed the button twice. On a slow page, some forms send the same sign-up or order twice.
  • Two copies of the same automation. Someone copied it to try a change, or moved it to a new account, and both copies are switched on.

The 10-minute check

1. Search for ten recent order numbers

Open the spreadsheet or list your automation writes to. Pick ten recent orders and search for each order number (Ctrl+F on Windows, Command+F on a Mac). If the search says "1 of 2", that order is in there twice.

No order numbers? Search for the customer's email address instead.

2. Count what three recent customers received

Search your sent emails, or your email tool's history, for three recent customers' email addresses. Count how many confirmations, welcome emails or receipts each one got. One of each is what you're hoping to see.

3. Look for automations that start from the same thing

List your automations and what starts each one, for example "a new order in my shop". Two automations that start from the same thing and do similar jobs are worth a question, even if they look different.

Don't forget the emails your shop, booking system or payment provider sends by itself. Those count too.

4. Look for the same order in two runs

Open the run history (Zap history in Zapier, the scenario's History tab in Make, Executions in n8n). Open a few runs around one of the doubled orders you found in step 1, and look at what went in. The same order number in two runs tells you the automation started twice.

Habits that keep every action to once

  • Look before adding. Ask whoever looks after the automation to have it search for the order number first, and only add a new row if it isn't there yet. All three tools can do this.
  • Check before running something again. When a run stops halfway, find out which steps already worked, and whether the step that "failed" actually went through, before anyone runs it again.
  • One job, one automation. When a replacement is built, switch the old one off the same day, and write down that you did.

What to do with what you found

If every order appeared once and every customer got one email, well done. Repeat the check after any new automation goes in.

If you found doubles, write down which orders, the dates, and which automations start from the same thing. That's exactly what whoever looks after your automations needs.

And if there's nobody to ask, I can look at it for you, read-only. Here's an example of the findings note you'd get.