> 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/how-input-fields-work/dropdown-field-behaviour.md).

# Dropdown Field Behaviour

This article explains how **dropdown fields** behave in Model Reef input screens.

You will learn:

* Where dropdowns appear in the interface.
* What kinds of choices they present.
* How dropdown selections affect model behaviour.

Dropdown fields are used for structured choices such as types, categories, branches and timing options.

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### Where dropdowns appear

Common places you will see dropdowns include:

* Variable type selection (Revenue, COGS, Opex and so on).
* Category and subcategory selection.
* Branch selection when assigning a variable to a branch.
* Timing options such as frequency or payment terms.
* Scenario, period and unit selection in some views.

Dropdowns keep inputs consistent by limiting choices to valid options.
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### Types of dropdown choices

Dropdowns may present:

* A fixed list of system defined options, such as variable types or frequency options.
* A list derived from the model, such as branches or existing categories.
* A combination of both, for example system options filtered by context.

In all cases, options are constrained to prevent invalid combinations.
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### How dropdowns interact with logic

Changing a dropdown value can have significant effects:

* Changing variable type alters how the variable flows through P\&L, Balance Sheet and Cashflow.
* Changing category or subcategory alters where it appears in reports.
* Changing branch moves the variable's contribution to a different part of the consolidation tree.
* Changing timing related dropdowns shifts accrual or cash patterns.

The system does not silently reinterpret values beyond these structural changes. The numeric time series stay the same unless directly altered.
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### Context sensitive dropdowns

Some dropdowns are context sensitive:

* The list of subcategories may depend on the selected category.
* Available branches may depend on permissions.
* Some timing options may only appear for certain variable types.

This helps keep choices relevant and avoids presenting options that do not make sense for the current context.
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### Validation of dropdown selections

Model Reef validates dropdown selections by:

* Ensuring combinations are allowed (for example Staff variables mapped to appropriate categories).
* Warning when a change could materially alter outputs, such as changing type from Opex to Asset.
* Preventing changes that would break core accounting rules.

You may see confirmation prompts for potentially disruptive changes.
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### Best practices

When using dropdown fields:

* Take care when changing structural fields such as type, category or branch.
* Use notes to document the reason for major classification changes.
* Review outputs after changes to confirm behaviour matches intent.

Dropdowns are powerful levers; using them consciously keeps models robust and traceable.
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***

## Related articles

* [Autocomplete Behaviour](/syntax/formula-syntax/autocomplete-behaviour.md)
* [Drilldown Behaviour](/syntax/chart-and-table-syntax/drilldown-behaviour.md)
* [Imported Variable Behaviour](/help/drivers-variables-and-timing/imported-variable-behaviour.md)
* [Build a Forecast Accuracy Tracker](/how-tos/scenarios-and-planning/build-a-forecast-accuracy-tracker.md)