Spreadsheet blunders aren't just frustrating personal inconveniences. They can have serious consequences. And in the last few years alone, there have been a myriad of spreadsheet horror stories.

In August 2023, the Police Service of Northern Ireland apologized for a data leak of "monumental proportions" when a spreadsheet that contained statistics on the number of officers it had and their rank was shared online in response to a freedom of information request.

There was a second overlooked tab on the spreadsheet that contained the personal details of 10,000 serving police officers.

A series of spreadsheet errors disrupted the recruitment of trainee anesthetists in Wales in late 2021. The Anesthetic National Recruitment Office (ANRO), the body responsible for their selection and recruitment, told all the candidates for positions in Wales they were "unappointable," despite some of them achieving the highest interview scores.

The blame fell on the process of consolidating interview data. Spreadsheets from different areas lacked standardization in formatting, naming conventions and overall structure. To make matters worse, data was manually copied and pasted between various spreadsheets, a time-consuming and error-prone process.

ANRO only discovered the blunder when rejected applicants questioned their dismissal letters. The fact that not a single candidate seemed acceptable for Welsh positions should have been a red flag. No testing or validation was apparently applied to the crucial spreadsheet, a simple step that could have prevented this critical error.

In 2021, Crypto.com, an online provider of cryptocurrency, accidentally transferred US$10.5 million (£8.3 million) instead of US$100 into the account of an Australian customer due to an incorrect number being entered on a spreadsheet.

The clerk who processed the refund for the Australian customer had wrongly entered her bank account number in the refund field in a spreadsheet. It was seven months before the mistake was spotted. The recipient attempted to flee to Malaysia but was stopped at an Australian airport carrying a large amount of cash.

In 2022, Íslandsbanki, a state-owned Icelandic bank, sold a portion of shares that were badly undervalued due to a spreadsheet error. When consolidating assets from different spreadsheets, the spreadsheet data was not "cleaned" and formatted properly. The bank's shares were subsequently undervalued by as much as £16 million.

The dark matter of corporate IT

The above is just a fraction of the spreadsheet errors that are regularly made by various organizations.

Spreadsheets represent unknown risks in the form of errors, privacy violations, trade secrets and compliance violations. Yet they are also critical for the way many organizations make their decisions. For this reason, they have been described by experts as the "dark matter" of corporate IT.

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