If I need to adapt a registred vendor invoice in a previous VAT period, I get the message: invoice can not be changed unless you change the VAT block date in the config. 

In the config, there is no such thing as VAT block date...? or it is well hidden. 

Has anyone seen it ?

I don't want to make credit memo and a new bill; I just need to change a line in a vendor invoice (without any VAT implication)

KR,

FHO;