Without accurate mileage figures and knowing the actual vehicle in which the journey was made, CO2 figures are a guess.

Our research showed that one local authority was overestimating their business mileage emissions by as much as 60%.
Whether driven by customers, procurement, legislation, shareholders, staff or conscience, most businesses and organisations have a requirement to reduce carbon emissions.
In England the Climate Change Act 2008 sets carbon reduction targets of at least 80% below the 1990 baseline by 2050. In Scotland the 2009 Climate Change Act adds a statutory target for reduction of emissions of 42% by 2020.
24% of all UK emissions are from transport, 90% of those from road transport.
The first step to reducing CO2 is to record a current baseline so that progress can be measured.
Many companies and organisations have this baseline, from which they have created carbon reduction targets.