Cede province vs Give core back

[Vladimiś]

Can someone tell me why getting core back gives me much more AE than just getting it back normal way? This makes no sense to me

[MhaelL']

I dont have the real answer to this, but the casus belli is reconquest, which mean that you used to have to control the provinces to get the back for discount on AE. Now you just need to control the fort. I'm not sure you need to control the fort for giving back cores wich is not in the casus belli anyway, so full AE.

[Kelldath]

Return core option in peace deals is not tied with many CB, thus usually ends up costing full aggressive expansion, while with the reconquest CB you get a 75% AE reduction for taking back your cores the normal way (cede province peace terms).

[Vladimiś]

But shoulndt reconquest cb give me reduced AE for acutally making them return the core to me. Unless they changed it in 1.16 or reconquest for vassal cores have different rules this makes no sense

[MhaelL']

Originally posted by Great Papyrus:

But shoulndt reconquest cb give me reduced AE for acutally making them return the core to me. Unless they changed it in 1.16 or reconquest for vassal cores have different rules this makes no sense

Reconquest for vassal if you mean using your vassal CB to attack actually require you to give the control of provinces to your vassal then asked for them to benefit of the AE reduction. Otherwise you will take full AE.

[Kelldath]

Originally posted by Great Papyrus:

But shoulndt reconquest cb give me reduced AE for acutally making them return the core to me. Unless they changed it in 1.16 or reconquest for vassal cores have different rules this makes no sense

It's a bit complicated, but reconquest gives you reduced AE when you re-conquer the land, meaning you're taking it back the usual way.

CB that give reduced AE for the diplomatic "return core" option are : Excommunication, Coalition, Colonial conquest and overseas expansion.
The first is hardly ever used, and the third and fourth are mean to give land back colonial nations or to future protectorates (to boost relationship).
The only real CB related to that option in the game is coalition war, since you're supposed to force the target to spit back everything he's taken.