Where should I include funder information in the DOI metadata?

If the resource being published received grant funding from a funder e.g The Seventh Framework Programme (European Union), this information can be included in the DOI metadata in the fundingReferences section.

Example:

<fundingReferences>
<fundingReference>
  <funderName>Seventh FrameworkProgramme</funderName>
  <funderIdentifier funderIdentifierType="Crossref Funder ID" schemeURI="http://doi.org/">http://doi.org/10.13039/100011102</funderIdentifier>
  <awardNumber awardURI="http://cordis.europa.eu/project/rcn/100180_en.html">282625</awardNumber>
  <awardTitle>MOTivational strength ofecosystem services and alternativeways to express the value ofBIOdiversity</awardTitle>
</fundingReference>
</fundingReferences>

In this case the funderIdentifier DOI is the Crossref Funder ID. Some funders may have multiple identifiers. For example the European Union has numerous funding mechanisms each with a separate DOI.

You can look them up here.