There is no legal IRS or any other organization (FASB, CASE, Sarbonnes Oxley, the new 990) mandated rule stating that you must keep copies of your checks or acknowledgements. You should have a data retention policy though. (new 990 suggestion for informational purposes)

That being said, you DO need to keep substantiation of restricted gifts, etc. We keep copies of all Reply devices and bundle them by date - if there is no reply device we make a copy of the check. We do not make copies of checks and attach them to the reply devices because this is a waste of staff time, supplies = MONEY)

For stewardship reasons we do keep copies of reply devices, correspondance, thank yous, etc. for donors in our major giving group of $1,000 and above. This is an internal policy for our major gifts folks but is not a requirement for audit or anything. Other organizations may define a major gift as $10K and above (Like the one my husband works for) or another dollar amount. All of our substantiation documentation is kept in hard copy files outside of RE. This is basically because of History going back to 1969 - unless we scanned all of the old historical backup we wouldn't have the donor files in a complete state in one place. (Would love to do this someday - maybe a great job for an intern to scan all of this stuff!)

If it's easy and fast, I don't see why you couldn't scan and keep them in the media tab. We don't have the luxury of the time and staffing levels it would take to do that. You may want to check some of the posts out that talk about the pros & cons of where to store the actual media files (linking them to an outside server or saving them on the RE server).

We do keep copy of checks until audit of that year is completed.  I often wonder if it's necessary but there have been things I've had to check.  Checks are filed with corresponding batch report.

We do not keep hard copy of acknowledgements/receipts, but rather a word file.  I run acknowledgements/receipts by batch so I just add batch number in file name and it provides an easy reference for letters we have sent (I can look up batch number on gift record and then open correct file).  We did remove the auto date function in the letters and I either edit document prior to running mail or do a replace all in the word document so that when file is opened at a later date, the actual date letter was sent is not automatically changed. We're relatively small an I can't imaging keeping hard copies of ours yet alone at the quantity of gifts some of you process.

Laurel, you said you keep "all reply devices".  Are you referring to a tear off part of a billing/solicitation appeal?  Do you keep these for things like an annual campaign?  We currently don't keep them and I'm considering if we should be.