> For the complete documentation index, see [llms.txt](https://help.taglo.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://help.taglo.io/variables/default-assumptions.md).
# Default Assumptions
How to use a Default Assumption to replace missing Assumptions
## Overview
You do not have to specify every [**Assumption**](/assumptions/introduction-to-assumptions.md) of an Assumption [**Variable**](/variables/variable-basics.md). For instance, you might have a Variable called `One-off costs`, as in the screenshot below. There are 20 periods in our [**Model**](/models/home-tab.md), but we only want to enter Assumptions for two of those periods, March and December 2025.
In this case, we can use a Default Assumption to provide a value for the other periods. The screenshot below shows that we have only selected 2 Assumptions in the [**Time Segment**](/variables/time-segments.md) **(1)**, but no warning is shown because we have added a Default Assumption that provides a value of `0` for any period without an Assumption.
Variable using Default Assumption
## Adding a Default Assumption
To add a Default Assumption, perform the following steps, as illustrated in the screenshots below.
* In the **Variable dialog**, navigate to the **Default assumption step** **(1)** (this will only be shown if `Assumption` Variable type is selected in the **Name and Setup step**
* If your Default Assumption does not already exist, ensure that the **Item statuses** table has its only cell selected **(2)**
* Click the **New** button **(3)**, which will open an [**Assumptions dialog**](/assumptions/assumptions-wizard.md) **(4)** in which to create the Default Assumption
* Enter any details and the value of the Assumption, click **Finish**, and the Assumption will be selected
