What Is a Plug in a Financial Model?
A plug in a financial model is a hardcoded number typed in to force two figures to agree, such as making a balance sheet balance or hitting a target total. Unlike a calculated cell, a plug does not flow from the model's logic, so it breaks the moment an assumption changes. Plugs are one of the most dangerous things hidden in a workbook.
What a Plug Looks Like
A plug is a constant sitting where you would expect a formula. Imagine a balance sheet that does not tie out by 250, and someone types 250 directly into the equity section so the totals match. That number looks fine on screen, but it is not connected to anything, so it silently holds the model together with tape.
Plugs also show up as overrides: a forecast cell that should read =PriorYear*Growth but instead contains a typed-in number because someone wanted a specific result for one period.
- A typed constant where a formula is expected.
- Often used to force a balance sheet to balance.
- Also appears as a one-off override of a forecast formula.
Why Plugs Are Dangerous
A plug breaks the link between inputs and outputs. When you change a driver, every formula updates, but the plug stays frozen at its old value, so the model quietly goes wrong without throwing any error. Because there is no #REF! or #VALUE! to catch your eye, a plug can survive multiple reviews undetected.
Plugs are especially harmful in models that get reused. A plug entered for one scenario stays put when the file is copied for a new deal, producing a number that looks calculated but is not.
- Plugs do not recalculate when assumptions change.
- They produce no error, so they pass visual review.
- Copied models carry old plugs into new work silently.
Finding Plugs and Hardcodes
The general technique is to hunt for hardcoded constants in places that should hold formulas, and to look closely at numbers embedded inside formulas, such as =Revenue*1.05 where the 1.05 should really be a driver cell. Native Excel can select all constants through Home > Find & Select > Go To Special > Constants, but that flags every label and legitimate input too, so the result is noisy.
Separating real inputs from suspicious plugs by eye across a large model is slow and easy to get wrong.
Go To Special>Constantsselects all hardcoded values at once.- It cannot tell a plug from a legitimate input.
- Numbers buried inside formulas like
*1.05are easy to miss.
Finding Hardcodes With ModelMint
ModelMint's Find Hardcodes locates the hardcoded numbers in your model, including constants where formulas belong and values typed into otherwise calculated cells. Surfacing them makes plugs and manual overrides visible so you can decide which are legitimate inputs and which are tape holding the model together.
It runs locally on Windows in Excel 2016 and later, with no telemetry, so you can audit a confidential model entirely on your own machine.
Find Hardcodes
Surface hardcoded numbers and plugs hiding where formulas should be.
Get ModelMint See how it worksFAQ
What is the difference between a plug and a hardcode?
A hardcode is any typed-in constant. A plug is a specific kind of hardcode entered to force two numbers to agree, like balancing a balance sheet. Every plug is a hardcode, but not every hardcode is a plug.
Why are plugs considered bad practice?
A plug does not recalculate, so when an assumption changes the model goes wrong with no error to warn you. It looks like a real number but is disconnected from the model's logic.
How do I find hardcoded numbers in Excel?
Go To Special > Constants selects all hardcoded values, but it cannot distinguish plugs from valid inputs. ModelMint's Find Hardcodes surfaces them so you can judge each one.