When a spreadsheet quietly becomes a liability

Every fragile system I’m called in to fix started as something reasonable. A spreadsheet that solved a real problem on a Tuesday. Then someone added a tab. Then a formula referenced another file. Then the one person who understood it left.

The tells

You don’t need an audit to know a spreadsheet has become a liability. You can feel it: nobody wants to be the one who opens it, changes are made by copying the whole file first, and the phrase “don’t touch the hidden tab” exists.

If a tool is too scary to change, it’s already broken — it just hasn’t told you yet.

What to do instead of a rewrite

The instinct is to rebuild everything in “real” software. Usually that’s wrong, or at least premature. Start by making the current thing safe: version it, add validation on the inputs that matter, and write down what each tab actually does. That alone buys you months of breathing room.

Then, and only then, move the riskiest piece — not the whole thing — into something more durable. Small, reversible steps. The goal isn’t elegance. It’s a system you’re no longer afraid of.