# Do I recalculate my base year if I sell, close or buy a unit?

Canonical: https://senseible.earth/answers/recalculate-base-year-after-selling-a-unit

Selling or buying a unit that existed in the base year is a structural change: recalculate the base year if the change passes your significance threshold. Closing a unit or opening a new one is organic decline or growth under the GHG Protocol, so the base year stays as it is.

## Which events trigger it

- Sell a unit: remove its base year emissions from the base year.
- Buy a unit that operated in the base year: add its base year emissions.
- Move an activity in or out, such as handing forging to a vendor or taking packing back in house: adjust the base year for that activity.
- Close a unit: no recalculation. The fall in emissions is real.
- Build or open a new unit: no recalculation. Its emissions are growth.
- Buy a unit that did not exist in the base year: no recalculation.

## The significance test

The GHG Protocol Corporate Standard, Chapter 5, asks you to set a threshold in advance and apply it every time. For validated targets, the SBTi's Corporate Near-Term Criteria require a recalculation policy with a threshold of 5% or less. Test each change on its own and all of a year's changes together against base year emissions.

## How to do it

1. Get the unit's emissions for the base year, built with the same method and factors as yours: its bills and invoices if the seller hands them over, or a clearly labelled estimate.
2. Recalculate the base year for the full year, as if the new structure had applied all along.
3. Restate every year shown in your trend the same way, so the series compares like with like.
4. Keep the original figures and disclose the reason, the threshold and both totals.

## What a deal file should include

Ask the seller for twelve months of electricity bills and fuel invoices for the base year as part of due diligence. Without them, you will estimate a figure you then have to defend to buyers and lenders for years.

## Illustrative year with a sale, a closure and a purchase

- Base year: 2,000 t CO2, of which Unit A 400 t and Unit B 100 t
- Unit A sold: 400 / 2,000 = 20%, above 5%, so remove it
- Unit B closed: organic decline, no change
- Unit C bought, operating in the base year at 150 t: 150 / 2,000 = 7.5%, so add it
- Restated base year: 2,000 minus 400 plus 150 = 1,750 t CO2

Figures are illustrative. 5% is the SBTi's ceiling; your written policy can set a lower threshold.

## What Senseible does here

Senseible keeps each unit's invoices and bills with their dates and factors, so base year emissions for a unit can be taken out or added from documents rather than estimates. Records can be kept per plant or GSTIN.

- [Recalculating when the grid factor changes](https://senseible.earth/answers/recalculate-past-years-when-grid-factor-changes)
- [SLL baseline after growth](https://senseible.earth/answers/sll-baseline-recalculation-after-growth)
- [Choosing a base year](https://senseible.earth/answers/how-to-choose-base-year-carbon-inventory)

Sources: [GHG Protocol Corporate Standard (2004), Chapter 5 Tracking emissions over time](https://ghgprotocol.org/corporate-standard), [SBTi Corporate Near-Term Criteria, base year recalculation](https://sciencebasedtargets.org)

Last reviewed 2026-10-18. SBTi 5%-or-less recalculation threshold checked 2026-10-19 against Near-Term Criteria; recheck when the Corporate Net-Zero Standard V2 criteria take effect.