My later mother passed away 10 years

maximum time for < impugnare una successione > ( = file an opposition to a succession has already occurred ) THEN YEARS , from from presentation day

I read on line that it's 5 years from when the Will is acknowledged by all heirs, is this correct? Is there a time limit?Thanks

https://www.e-glossa.it/wiki/prescrizione_del_diritto_di_accettare_l'_eredit%C3%A0.aspx Ai sensi dell'art. 480 cod.civ., il diritto di accettare l'eredità si prescrive in dieci anni. Il dies a quo coincide con il giorno dell'apertura della successione o, nell'ipotesi di istituzione d'erede sottoposta a condizione sospensiva, dal giorno in cui si verifica l'evento che determina l'efficacia della delazione ereditaria. Ciò si spiega agevolmente, considerando che soltanto quando si sia verificata la condizione sospensiva diviene attuale la delazione nei confronti dell'erede istituito sub  I suggest you to use a NOTARY for this  http://www.notariato.it/en Ugo, by Lifeinitaly.it see >  

If it is one of the heirs that was cited in the will and the succession has been done that I would assume that the heir in question would have already accepted/not accepted the succession.    If they accepted and have now changed their mind it becomes a lot more complicated.   You need to talk a notaio.  There are Italian notaries in the UK if you are there, at least 2 in London that I know of.  

Italian Notary in London http://www.leonenotaries.com/index.html 

Hi Ugo.Thank you for reply, much appreciated. Yes, my sister was cited on the will but with the legal minum requirement under Italian law. The Successione was passed a few years ago and she has never declined it. My sister is challenging the will due to the fact that myself and my brother were nominated as executors with the 'porzione disponibile' My sister is challenging the will on medical grounds. I hope that this has put more light on the situation.