Constructed figure, assumptions listed

There is a person, in your company, who runs a system your invoicing depends on. You know who.

They haven’t asked for anything, they aren’t making any threats, and that’s precisely why the subject is never addressed.

The calculation, with its assumptions on display

A position paid at the market median, 55,000 euros gross, costs 78,546 euros a year once the employer coefficient is applied, that is 6,546 euros a month.

The day this person leaves, continuity runs through an external service. At the reference daily rate, over 20 working days, full-time cover costs 11,500 euros a month.

LineMonthly amount
Cost of the occupied position€6,546
Cover by full-time service€11,500
Monthly extra cost of the dependency€4,954

Three months of vacancy come to 14,862 euros. Six months, 29,724 euros. Twelve months, 59,448 euros.

Why this figure is a floor

The calculation assumes a contractor can take over the system. On an undocumented system, they can’t, or not before several weeks they will bill you for.

It also assumes immediate availability, whereas an emergency engagement is priced above the reference rate.

The real amount exceeds 4,954 euros a month. This one has the advantage of being reconstructed from public sources and written assumptions, which makes it defensible in a committee meeting.

The three possible answers, and their price

Document. Two to five days of guided work from the person concerned: what the system does, what breaks it, who to call, where the access credentials are. At 360 euros for an internal working day, full coverage comes to under 1,800 euros, that is eleven days of position vacancy.

Double up. A second person, even partial, even junior, able to get into the system. The cost is real and recurring, the dependency disappears.

Accept it. That’s a legitimate decision provided it’s made with the figure in view and written down somewhere. An accepted, provisioned risk is not the same object as an ignored one.

What you will be told, and what to answer

“She won’t leave.” The question isn’t departure, it’s absence. A two-month sick leave produces the same bill as a resignation, without a notice period to plan for it.

“We’ll document after the next project.” Documentation done after departure costs the rate of the contractor who reconstructs it. Done beforehand, it costs the internal rate. The ratio is about one to one and a half, and one of the two cases produces nothing reliable.

“She’ll refuse to document it.” That’s a signal, not an obstacle. Someone who refuses to hand over knowledge has understood that their value lies in their internal scarcity, and that’s exactly the situation you’re trying to get out of.

“We don’t have the budget to double the position.” Doubling costs half a position. Not doubling costs 4,954 euros a month the day it happens. The calculation depends on the probability you assign to that day, and that probability isn’t zero.

To check for yourself, in twenty minutes

The list of systems held by a single person. Write down the names. The discomfort of writing a name down is itself information.

The date of each of these people’s last long absence. What happened then is your best estimate of what will happen next time.

The state of access credentials. If a single person holds an admin password, the dependency is no longer just operational, it’s legal.

The cost of documentation. Two to five days, at your internal daily cost. Compare it to a month of position vacancy, and the decision makes itself.

The sentence to remember

A dependency on a single person isn’t a human risk. It’s a monthly line you aren’t paying yet.

Open in a spreadsheet · The monthly extra cost, as a spreadsheet (733 bytes)

Sources

Last reviewed: 20 August 2026

Figures to review before 20 August 2028