DCS is a separate, mandatory regulation on IMO-level with separate documentation requirements, due dates and principles. In general, DCS requires less data then MRV (i.e. no cargo, no voyage list). Clients reporting their voyage data to DNV for MRV are also fulfilling the reporting requirements for DCS, assuming reporting is done throughout the year.
The EU is currently considering this and is expected to come up with a proposal that will be considered on political level in 2019. DNV expects partial harmonization at best.
DNV is offering one combined reporting format covering both MRV and DCS. Customers are advised to contact their customer support to ensure the contract covers the needed verification service scope, i.e. that DCS is also covered.