Choosing Carbon Credit Vintage and Volume for Your Purpose

How to pick a vintage and the right number of tonnes for a voluntary goal or a CORSIA obligation, when to buy in tranches, and how to avoid buying too much or too little.

Two numbers appear on every requirement we receive: a vintage and a volume. Buyers often settle both quickly, then find later that the vintage did not suit their policy or that the volume left them short at year end. A little thought at the start avoids both problems.

What vintage means

A credit's vintage is the year in which the emission reduction or removal took place. It is not the year the credit was issued or the year you buy it. A 2022 vintage credit may be issued in 2024 and sold in 2026.

Every listing on our marketplace shows the vintage alongside the volume, registry and delivery type. For forward lots, the vintage may refer to a year that has not yet been verified, which affects risk and timing; our page on spot, issued and forward credits explains the difference.

Choosing a vintage for a voluntary goal

There is no single correct vintage for voluntary buyers, but a few principles help.

Stay reasonably close to the emissions you are covering. If you are compensating for emissions in your 2025–26 financial year, recent vintages tell a cleaner story than credits from a decade ago. Many corporate buyers set a rolling window, such as no older than five years before the reporting year. Whatever window you choose, write it into your purchasing policy so it is applied consistently.

Expect older vintages to need more explanation. Older credits are often cheaper, partly because some buyers worry that the methodology or baseline used at the time would not be accepted today. That is not automatically a problem, but your due diligence should look at whether the project's approach still stands up.

Check what your reporting framework or customer expects. Some frameworks, labels and procurement contracts set their own vintage limits. If a large customer is asking you to offset a product's footprint, ask them what they accept before you buy.

Choosing a vintage for CORSIA

For airlines and aircraft operators, vintage is a rule, not a preference. Eligible emissions units must come from an ICAO-approved programme and fall inside the eligible vintage window for the compliance period, and units for current periods must carry host-country authorisation and a corresponding adjustment. These conditions are set by ICAO and can change, so always confirm against the current documents on icao.int before committing. A unit outside the window is not usable for compliance, however good the project.

When you post a requirement on our intake platform, you can state CORSIA conditions alongside accepted programmes and vintages, which lets us filter out unsuitable lots early. The CORSIA eligible units checklist covers the other tests.

Working out the volume

Voluntary buyers

Start from a measured emissions figure, not an estimate made in a meeting. Then decide what share you are covering:

Take your inventory total for the scope you are addressing, in tCO₂e. Suppose a Bengaluru software firm's business travel and office energy come to 3,400 tCO₂e.
Decide the share you will compensate. If the firm commits to covering all of it, the target is 3,400.
Allow for revisions. Inventories are often restated after assurance. A small buffer, or a plan to top up, is sensible.
Round to lot sizes. Listings show available volume; you may need to combine lots.

CORSIA operators

The volume is driven by the offsetting requirement, which depends on your emissions from covered international flights, the growth factor published for the relevant year, and any reductions claimed from eligible fuels. From 2024 the baseline is 85% of 2019 emissions. Our calculator estimates the requirement from fuel burned or from CO₂, using a growth factor you enter, and lets you deduct eligible-fuel reductions. Treat its output as a planning estimate; the final figure comes from your verified report and your national authority.

Buying in tranches

Buying everything at once is simple, but it is not always wise. Splitting a purchase into tranches can help when:

your emissions figure is not final. Buy a firm portion now and the rest after the inventory is assured.
you want price averaging. Spreading purchases across the year reduces the risk of buying all your volume at a high point.
you want variety. A first tranche of removals and a second of reductions, or credits from two categories, can spread project risk.
forward supply is involved. If part of your volume comes from forward lots, a spot or issued tranche covers you if delivery slips.

For CORSIA, align tranches with the compliance-period cycle so you are not left buying under time pressure near the cancellation deadline.

Avoiding overbuying and underbuying

Risk	Common cause	How to avoid it
Underbuying	Using last year's inventory without growth	Build in expected growth, or plan a top-up
Underbuying	Forward lot delivers late or short	Cover part of the need with issued units
Overbuying	Inventory restated downward after assurance	Buy a firm share first, the rest later
Overbuying	Bulk discount tempts a larger order	Buy only what your policy and plans can use
Wrong units	Vintage or eligibility not checked	Write criteria down before choosing lots

If you do end up with surplus units in your own registry account, they can usually be held for a later year, provided they still meet your criteria then. Credits retired on your behalf cannot be reused, so get the number right before retirement. Our page on registry accounts for buyers covers that choice.

Once you have a vintage window and a target volume, filter the marketplace by registry and delivery type, or send the figures to us and we will shortlist lots that match.