# Does our target base year have to be the same year as our inventory base year?

Canonical: https://senseible.earth/answers/ghg-target-base-year-same-as-inventory-base-year

No. The two may differ, but using the same year usually streamlines reporting. Whichever year you choose for the target, its emissions data must be reliable and verifiable. The standard also allows a multi-year average as the target base year.

## What the GHG Protocol says

- It is possible to use different years for the inventory base year and the target base year.
- To streamline inventory and target reporting, it usually makes sense to use the same year for both.
- Data for the target base year must be reliable and verifiable.
- A multi-year average target base year is possible, on the same considerations as for an inventory base year.

## When to split them

Split them when your oldest year has weak records. Pick the earliest year where every fuel and electricity figure traces to a bill or meter, and use that as the target base year. Keep the inventory base year as it is, so past reports stay comparable.

## When a multi-year average helps

If one year was unusual, such as a shutdown or a one-off order, averaging two or three years gives a steadier starting point.

## What stays the same

Recalculation rules for structural change and method change still apply to a fixed target base year, as chapter 5 describes.

## Example with made-up numbers: a three-year average

- Inventory base year: FY 2019-20, kept as is for past reports.
- Target base year, average of FY 2022-23, FY 2023-24, FY 2024-25: 410 t, 450 t and 430 t.
- Average: (410 + 450 + 430) / 3 = 430 t.
- A 20% cut then means a goal of 430 x 0.80 = 344 t.

Example only.

## What Senseible does here

Senseible builds each month's energy and emission figures from the bills, so a target base year can be chosen from the first year where every line has evidence.

- [Recalculating when the grid factor changes](https://senseible.earth/answers/recalculate-past-years-when-grid-factor-changes)
- [When targets must be recalculated (SBTi)](https://senseible.earth/answers/sbti-target-recalculation-triggers-5-percent)
- [Carbon number for MSMEs](https://senseible.earth/msme-carbon-number)

Sources: [GHG Protocol, Corporate Accounting and Reporting Standard, chapter 11 (Setting a GHG target)](https://ghgprotocol.org/sites/default/files/standards/ghg-protocol-revised.pdf)

Last reviewed 2026-11-03.