When spreadsheets stop being enough.

The signs, in the order they usually appear

First, someone becomes the person who "knows the file". Then a number has to be entered twice, in two places, to stay correct. Then a month closes late because two reports disagree and somebody has to find out which is right. By the time a customer is told the wrong stock figure, the spreadsheet has stopped being a tool and become a risk.

Stock is where it breaks first

A spreadsheet cannot tell you what is reserved as opposed to what is on the shelf. As soon as you have more than one warehouse, goods in transit, or an order picked but not yet shipped, the difference between physical stock and available stock stops being academic. That gap is what gets sold twice.

The second sign: nobody can answer "how did we get this number?"

A ledger that is a spreadsheet has no history. When the year-end figure is questioned, the honest answer is often that nobody knows what the cell contained in March. A double-entry ledger is not bureaucracy — it is the ability to explain a number six months later, which is the whole point of accounting.

What a system has to earn

• One place a customer, product or invoice exists, referenced everywhere else rather than copied.
• Stock that knows the difference between on hand, reserved and incoming.
• A quote that becomes an order, and an order that becomes an invoice, without anyone retyping the lines.
• A real ledger underneath producing statements you can hand to an accountant unedited.
• Several companies or currencies if that is where you are heading.
• An audit trail, so a changed price has a name and a time against it.

What you give up, honestly

You give up the freedom to type anything into any cell. That freedom is exactly what made the spreadsheet fast and exactly what makes it unreliable at scale. A good system should feel slightly stricter and considerably calmer. If it feels slower at everything, it has been configured wrong or bought too early.

Do not migrate everything

The most common failure is trying to move five years of history on day one. Move the open items — current stock, unpaid invoices, active orders — and keep the old files readable. Anything else can be looked up in the archive on the rare day it matters.