# Default Assumptions ## Overview You do not have to specify every [**Assumption**](https://help.taglo.io/assumptions) of an Assumption [**Variable**](https://help.taglo.io/variables). For instance, you might have a Variable called `One-off costs`, as in the screenshot below. There are 20 periods in our [**Model**](https://help.taglo.io/models), 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**](https://help.taglo.io/variables/time-segments) **(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.

## 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**](https://help.taglo.io/assumptions/assumptions-wizard) **(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