The 6 months lead time is to provide sufficient time for MHD to assess your safety case, which comprises document reviews and on-site verifications.
Safety case clarifications will be requested of the MHI, where necessary.
MHI registration would be granted after your safety case is assessed.
Safety cases for large MHIs with complex processes may require assessment at a much earlier stage.
You will be informed in advance to facilitate the assessment process and to prevent delays in registration.