The maximum mass balance period shall be three months (a shorter period is possible). Does this mean that System Users have to sell all certified material within this timeframe?

No, the certified material does not need to be sold within three months. Positive credits can be transferred from one mass balance period to the next as long as the certificate is valid and, for ISCC EU, as long as at least the equivalent amount of the specific raw material or product (sustainable or non-sustainable) is physically in stock. However, it is not allowed to sell more sustainable material than received in stock (go negative) at the end of each mass balance period.

For producers of agricultural biomass (farms/plantations) or forest biomass and first gathering points sourcing only agricultural biomass or forest biomass, the mass balance period shall be twelve months (or shorter).