Download the corrective affidavit from the revenue website, executor/adminsitrator fills it in, get it sworn, post with copy to revenue. When it comes back check the probate office website to see if the additional money will result in more fees. Phone the probate office to see if they will take the affidavit and cheque by post, I think they will but I'm not 100% sure. Chances are there wont be any more fees to be paid, so you just need to send them the affidavit so they can note it. I don't see any problem with collecting and distributing the money while waiting for the paper work to go back and forward