> For the complete documentation index, see [llms.txt](https://help.modelreef.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://help.modelreef.io/syntax/scenario-syntax/overriding-drivers.md).

# Overriding Drivers

This article explains how to **override drivers** between scenarios in Model Reef.

You will learn:

* How drivers behave when each scenario is a separate model.
* Which drivers are natural levers for scenario design.
* How driver overrides cascade into many dependent variables.

Drivers are often the cleanest levers for exploring scenarios because they feed multiple variables at once.

## 1. Drivers per scenario model

Each scenario model has its own copies of all drivers:

* Economic drivers such as inflation, prices, FX and macro indices.
* Operational drivers such as units, volumes, utilisation and headcount.
* Modifier drivers such as growth rates, scenario multipliers and stress factors.

Editing a driver in one scenario does not change it in others.

## 2. Common driver overrides

Scenario modelling commonly involves changing drivers such as:

* Revenue growth or demand drivers.
* Customer acquisition or churn rate drivers.
* Price escalation or discounting drivers.
* Cost inflation or efficiency drivers.
* FX rate paths or commodity price series.
* Capacity or utilisation drivers for staff, plants or fleets.

Changing a driver can reshape many variables and branches simultaneously.

## 3. Overriding a driver in a scenario

{% stepper %}
{% step %}

### Open the scenario model

Open the scenario model you want to change.
{% endstep %}

{% step %}

### Edit the driver

Open the **Driver Editor** or the associated Data Library entry. Edit the time series, preset, forecast method or modifiers.
{% endstep %}

{% step %}

### Save

Save the changes.
{% endstep %}

{% step %}
All variables in that scenario model which reference the driver will update automatically.
{% endstep %}
{% endstepper %}

## 4. Understanding impact across the model

After changing a driver:

* Revenue, cost or other variables driven by it are recalculated.
* P\&L, Balance Sheet, Cashflow, Cash Waterfall and valuation outputs change.
* Dashboards and reports for that scenario reflect the new assumptions.

Use dashboards and comparison views to see how an override changes the overall picture relative to other scenarios.

## 5. Documenting key drivers

For clarity and governance:

* Add notes to key drivers describing their role and scenario specific values.
* Tag core scenario drivers (for example `Key scenario driver`).
* Maintain a simple list of which drivers differ by scenario when preparing board or investor material.

This helps stakeholders understand the storyline behind each scenario.

## Related articles

* [How to Enter Drivers](/syntax/how-input-fields-work/how-to-enter-drivers.md)
* [Overriding Variables](/syntax/scenario-syntax/overriding-variables.md)
* [Operational Drivers](/help/drivers-variables-and-timing/operational-drivers.md)
* [Operations & Unit Economics](/how-tos/operations-and-unit-economics.md)