As a side note: The question was raised as to whether SSN is a natural or synthetic key. As a firm believer in Albert Einstein's ideas (mostly), my answer is "It's all relative." If YOU are the person working for the agency that issues SSNs, it is synthetic. To anyone else, it is natural because you didn't synthesize it. Don't forget that SSN actually is encoded. First 3 digits = geographic. Next 2 digits = ID of an issuing group/authority. Last 4 digits = autonumber.
As to the auditor question: there are ways around the non-contiguous number issue, but the simplest way is to use some variant of the DMax+1 scheme OR to document that an aborted autonumber index is neither stored nor re-used in Access. Good auditors understand the concept of mitigation and would know about non-contiguous numbering as a property of the indexing system. What you would have to do for auditors in that case is to have a separate logging table for what got stored.
Here is a counter-example. We can have long sequences on our system where nothing happened. Our timestamps in the log file are discontiguous but they didn't miss anything. OK, I know it is a stretch, but auditors who kvetch over a known discontiguous number method are just as unimaginative and humorless as those who kvetch over idle gaps in an audit log's time stamps. (Wait... unimaginative and humorless? They must be the Men in Black.)
Seriously, really GOOD auditors will ask for a system design document first before they look at what is on the system. If this design document says "this number will be increasing but not contiguously so" AND the system owners signed off to this document, the auditors can be literally told to shut up and do something constructive. No, I'm not being flippant. This is also why, if you look at documentation for fiduciary systems, they often refer to some external standard for such systems - which would have prevented you from picking that discontiguous situation in the first place. I guess what I'm saying is that in the world of business, if regulations allowed the numbering scheme to have gaps, then the "auditors" argument is moot. If regulations forbade it, you would not have chose that situation anyway.
