A Principal Investigator (PI) can submit a proposal to the SyG call for proposal if their existing ERC project ends no more than two years after the SyG call deadline (cf. ERC Work Programme 2019, section Restrictions on submission of proposals). For the SyG 2019 call, this means that the ongoing Grant has to end before 8 November 2020.
A PI may hold only one ERC grant at any time. A new frontier research project can only start after the duration of the project fixed in a previous frontier research grant agreement has ended (cf. ERC Work Programme 2019). These eligibility requirements regarding grantees are the same as for the other frontier research grants.