# Line-items
URL: https://docs.valsight.ai/line-items/
Description: Line-items are the smallest unit of change in a simulation. Each line-item defines how the value of a single node is adjusted within an assumption.
Line-items are the smallest unit of change in a simulation. Each line-item defines how the value of a single node is adjusted within an assumption.

## Why it is relevant

* Makes changes to model drivers explicit and controllable
* Supports granular, targeted simulations
* Keeps alternative assumptions comparable and transparent

## How it works

A line-item represents **one concrete change to one node**.

Each line-item:

* Is always assigned to exactly one assumption
* Affects exactly one simulation-enabled node
* Describes how that node’s values change (absolute or relative)
* Can be filtered to apply only to specific parts of the data

By combining multiple line-items within an assumption, complex simulations can be built from small, explicit changes.

![Line-items.png](./images/6664519692.png)

Line-items can also have **variants**, allowing alternative versions of the same change (for example optimistic vs. pessimistic).

## Using the feature

* Use line-items to express precise changes to individual drivers.
* Combine multiple line-items to represent a broader assumption.
* Use variants to model mutually exclusive alternatives.

## Characteristics

* Line-items can only change simulation-enabled nodes.
* Line-items do not exist on their own; they always belong to an assumption.

## Access & permissions

Line-items follow the same permissions as assumptions and scenarios.
Users who can edit assumptions can create and modify line-items.

## FAQ

**What is the difference between an assumption and a line-item?**

An assumption groups changes conceptually, while line-items define the individual changes.

**Can a line-item affect multiple nodes?**

No. Each line-item applies to exactly one node.

**Can line-items be reused?**

Yes. Line-items can be duplicated and adapted.

**Are line-items optional?**

No. Every assumption is built from one or more line-items.

## Related documentation

* [Assumptions](/assumptions/)
* [Line-items](/line-items/)