You may be able to have uncashed checks reissued. I believe it's up to the previous 7 years and they may require you to send them the expired ones. In any case, I would call the IRS at 1-800-829-0922 and find out directly from them their procedures on reissuing. You may also want to have your uncle sign off on a power of attorney form (form 2848) so you could discuss the matter on his behalf with the IRS. Good luck!