> For the complete documentation index, see [llms.txt](https://kb.bravegen.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://kb.bravegen.com/carbon/configuration/reporting-settings/base-year.md).

# Base Year

Select, set, and update a base year in BraveGen Carbon.

## Choosing a base year

The GHG Protocol Corporate Standard does not mandate a specific base year. Choose a year using a defensible, documented method. Apply consistent recalculation rules.

Choose a year that meets these criteria:

* **Reliable data** — You can verify activity data and emission factors with reasonable confidence.
* **Representative performance** — Avoid anomalous years. Major shutdowns, divestments, or one-off events can distort the baseline.
* **Aligned reporting cycles** — Choose the earliest year with complete data. Alternatively, align it with a fiscal year, science-based target, or regulatory requirement. Many SBTi submissions expect a base year within two years of target setting.

Common choices include the first year with complete Scope 1 and 2 data. Include Scope 3 when available. You can also use a year required by CDP, SBTi, or local regulation.

#### Split Base Years

BraveGen Carbon supports separate base years for each GHG scope. The GHG Protocol does not require one base year for all scopes. This approach is common when Scope 3 data becomes reliable after Scope 1 and 2 data.

Use split base years when:

* Scope 1 and 2 data, such as fuel and electricity, is available earlier.
* Scope 3 data needs more time to mature. It may use value-chain estimates, supplier data, or spend-based factors.
* A single base year would delay Scope 1 and 2 reporting. It could also create a low-quality Scope 3 baseline.

SBTi and CDP accept different base years by scope. SBTi often expects a later Scope 3 base year.

***

### Set or update the base year

Only Administrators can set the base year. See [User Roles](/carbon/configuration/user-management/user-roles.md).

Go to **Settings → Carbon Configuration → Reporting** and select the edit icon beside **Base Year**. The row summarises the current selection for each scope, for example *Scope 1: FY22, Scope 2: FY22, Scope 3: FY24*.

| Field                   | Description                                                                                                                                |
| ----------------------- | ------------------------------------------------------------------------------------------------------------------------------------------ |
| Scope 1 Base Year       | The period to use as the base year for Scope 1. Listed as the financial year and its date range, for example `FY22 (Apr 2021 - Mar 2022)`. |
| Scope 2 Base Year       | The period to use as the base year for Scope 2.                                                                                            |
| Scope 3 Base Year       | The period to use as the base year for Scope 3.                                                                                            |
| Rationale for selection | Your justification for the years chosen. Minimum 40 characters. Disclosed in your audit trail.                                             |

Select **Recalculate Base Year** to apply the selection, or **Cancel** to discard it. The button is named for what it does: applying a base year restates the figures every comparison, target, and trend in the product is measured against.

{% hint style="warning" %}
Changing the base year changes your reported performance against every existing target and comparison. Only update it under your [recalculation policy](/carbon/configuration/reporting-settings/base-year/base-year-recalculation-policy.md), and record the reason in the rationale.
{% endhint %}

{% hint style="info" %}
BraveGen Carbon does not currently support rolling base years. Contact our support team to register interest in this feature.
{% endhint %}

***

### Write the rationale

The rationale is a disclosure included in your [audit trail snapshots](/carbon/audit-trail/snapshots.md). Write it for an external auditor or verifier.

Cover:

* Why each year was selected, and why split years were used if the scopes differ.
* What makes the data for those years reliable and representative.
* Where a change is being made, what triggered it under your recalculation policy.

***

### Activity Log

Every change to the base year is recorded in the **Activity Log** on the dialog, with the user, the timestamp, and the rationale supplied at the time. Users can reply to an entry to add context, and pin an entry to keep it at the top.

A restated base year is one of the first things an auditor looks at. The log is the evidence that each restatement was made under your policy rather than to improve a trend.

***

### Setting a recalculation policy

Set a base year recalculation policy after selecting your base year.