CofA within EASA member states

AJ wrote:

When a certified plane (< 2T) has been registered in one EASA member-state, then gets sold to another EASA member-state for future registration …

Note that, at least within the EU, the new owner can keep the old registration. The old registry may require a local contact. E.g. NL does, FR doesn’t. Note also that in theory the registration cannot be refused for stuff like “STC is not EASA approved” (since in theory it was checked in the previous register), neither can (within the EU) the VAT status of the plane in the past be a blocker (since the previous register is supposed to have checked the VAT status). The VAT questions on the sale happening now are within scope, obviously :)

• does one still need and use an export CoA for this, or is this no longer needed?
• if not what paperwork is used these days ?
  

No export CoA; but a a proof of deregistration from the previous register, a valid ARC, etc?

can one legally fly with this export CoA (or whatever is used these days) until it expires (after 1y I presume), and then only apply for the new ARC ?

I don’t expect so.

or is the plane grounded after export and until the new registration has taken place ?

My understanding is that it is grounded after deregistration, which need not happen at the same time as the export, nor at all (within the EU).