You CAN unvoid a transaction that has already been voided !!!
I wanted to give this answer to the question regarding how or if you can unvoid a previously voided transaction. I have a lot of old credit card expenses sat unreconciled and contiually being brought forward on every reconiliation that relate to a previous accounting year/s. Whilst trying to work out how I get rid of these without affecting my card balance or the PL (which I still haven't at the time of writing this :-/ Any solutions would be gratefully received!) I decided to see what would hapen if I voided one. The effect was that it created a NIL on the bank but also removed it from the PY Profit & Loss and reversed it on the next VAT as an exceptional item on the current VAT. Not what I wanted. I had read you couldn't unvoid a void transaction so I decided to open the voided now nil transaction and re-insert the original figures. Lets see what happens again I thought!!! To my surprise it actually completely reinstated my voided transaction back to it's former postion in it's entireity! Back on the PY profit & loss, removed from the current VAT and back to unreconciled on the bank. Boom!! Hope this helps anyone with the same issue