Mobilisation requires that everyone’s decisions are informed by carbon on their invoices, but also that every person and every institution has a view of their annual climate contribution to the collective Trajectory, so that they can continuously improve it. Carbon on invoices provides the necessary information to individuals.

The overall footprint of a person or household is the sum of their footprints in their different roles.

A person or household can be a producer (if it is an independent entrepreneur), a consumer and a financier (through its financing in its current account, its savings).

The footprint of a household is the footprint of the products and services it purchases in a year.

This footprint is known to him if the advertising rules are modelled on those of prices: whenever the price is mentioned, the footprint must also be mentioned (see Carbon advertising).

It is only displayed at the distribution stage by producers when the carbon footprints of the products are sufficiently complete (see Start-up and ramp-up).

The overall contribution of a person or household is also the sum of the contributions in its different roles. Bank statements give each consumer the footprint of his or her consumption and therefore its variation over the previous year : it is sufficient for electronic card payments to include the footprint of what is paid. This variation is his annual contribution to the Trajectoire 2050. Each individual is made responsible for preferring the same product with less carbon (one pot of yoghurt rather than another…) or for replacing one product with another that has less carbon (saving money by driving less quickly…).

Example: a consumer has a footprint of 11.2 MtC in 2021 and 11.3 MtC in 2022. His annual target contribution to the 2022 trajectory is a degradation of 0.1 MtC. If electronic invoices (soon to be generalised) include the carbon footprint, it will be easily transmitted to the final consumer, excluding cash payments. More extensive adaptation of payment software is necessary if we wish to recover all the carbon lines of a payment at the supermarket checkout. And mechanisms need to be devised when a carbon expenditure has effects over several years (car, housing, etc.), since private individuals do not have accounting systems that allow them to track the carbon content of an investment over time.

Its contribution to consumption is equal to the variation from one year to the next of the footprint of its consumption. It can be a service of a payment operator that accumulates the different footprints over time and presents them in an educational way.

This contribution is complemented by a savings footprint that aggregates the carbon contribution of each investment held by the household (see The climate contribution of finance).

Households also buy capital goods, notably cars and housing. These pose measurement problems, as a household does not have an accounting system that allows it, like a producer, to spread the footprint of the capital good over several years,

• • spread the footprint of the capital good over several years
  • and to attach to the asset the carbon footprints it generates for its operation: maintenance, improvement, extension or heating work for a house, maintenance and fuel for a vehicle.

One approach is to associate a sustainable carbon label with each car capital good, indexed on an existing public identifier (perhaps the registration number for a vehicle, the mortgage number for a house). This label records the carbon flows associated with the equipment with several objectives,

• • To allow the household to track its footprint annually and over time,
  • To enable them to measure the actual carbon footprint of the equipment over time and make better maintenance or renewal decisions
  • Allow the manufacturer to measure the actual carbon efficiency of the good produced.

These sustainable carbon labels should therefore be stored in secure, anonymised repositories that allow researchers and producers to optimise carbon footprints.

Start, Primary carbon, Electricity, Accounting framework, Customs scale, Carbon disclosure, Software, Contributions to the trajectory : Companies, Finance, Individuals, Territories