In Chile we have a tax on fuel that changes every week. It is defined as a certain amount of UTM (UTM is a currency that changes monthly with inflation) per m3, and this amount changes every week. You can find the values every week in http://www.sii.cl/valoresyfechas/mepco/mepco2020.htm.

Due to the tax definition, the percentage per litre changes slightly every week. The ideal solution would be to set a scheduled request to an API to set the percentage, but I can't find an option to automate that task. The other way would be to manually enter that tax when someone registers an expense (every ticket has the amount detailed), and we tried to add it as another field, but it doesn't reflect in the cost analysis as a tax.