(note - The AccountingFirm time is very much in the past tense)
The Audit Trail has nothing to do with being audited, nor with keeping people honest. It "audits" in the sense that it records every completed/cleared transaction that takes place in the file, including deleted ones. NOTE -- non-posting transactions are NOT recorded (estimates, etc) because they do not actually affect any accounts.
The basic/free-or-dirt-cheap version are the "For Dummies" ones (extreme restrictions on creating Items/accounts, etc), and I would not recommend them for anything bigger than personal finances. The $200ish one (at the time) was QB pro or PT "standard". IIRC, they had Audit Trail but they may or may not have been accessible.
Fun Fact -- Every version of QB short of Enterprise (uses SQL Server, iirc) and ALL versions of PT use the same files -- the Accountant's Edition of either can read and manipulate lower-level files without forcibly upgrading them to the more expensive version. Invaluable tech support tool. We also used it for things which were impossible in lower versions, as the changes stick (e.g.: QB Basic/SS cannot create Service Items (or was it Non-Inventory Items??) -- open a SS file in Accountant, create the items, and switch back to SS: the items will be there and usable)
At least for QB, as of...I wanna say year 2008 or later (?), it became impossible to turn of off the Audit Trail or remove anything from it by any means short of using Clean Up Data (read: purge and condense). To the best of my recollection, however, even that would simply make it so that the Audit Trail was viewable, but purged transactions would simply not be "clickable/no way to "zoom to the transaction" because it's not there anymore. In older editions, yes, Cleanup ("Condense" for v2000 and prior) would actually delete the AT, and it was possible to simply turn it off at that time. Keep in mind that this process is NOT something you can do accidentally -- no keyboard shortcut for it, Admin only, nobody else can be logged in, and it warns you multiple times what you're about to do....and it takes FOREVER, even if the data is local.
As for mistakes ... ? Really just the audit trail. Not sure how a program can prevent mistakes, EXCEPT for the fact that both of them force you to use double-entry accounting, and they at least try to facilitate GAAP. In ooold versions of either, however, it was possible to make one-sided entries. The existence of such entries in modern versions will actually break/corrupt the file, for those who have grandfathered them in. As for fraud: Really just the AT, afaik. While even $200 feels like a lot to me for a computer program
, for accounting software, that's chicken feed.
The business gets what it pays for....but heck, we were willing to sell it to them and fix it when it went kaboom. ~_~ These progs being cheap are part of why they're overwhelmingly popular. The ones that babysit you start at ten to twenty times the price.
On that note .. QB doesn't go boom nearly as often, but it also had fewer built-in options with which to fix said issues. PT has really good built-in fixer options (must be enabled via the command line, for good reason), but it also NEEDS them more often. It's also more susceptible to network hiccups/configuration errors and just plain going kaboom.
Sadly, PT has a long standing glitch when doing a year-end Close, which was still in effect as of two years ago, where a critical, "HAHAHA YOU BE F$%@ED, SUCKA! Delete the file and restore that backup we just forced you to make" message would always be immediately followed by one that read "The Close has completed succesfully". The first message was accurate. We got plenty of calls from people who assumed the opposite and didn't ask anyone about it...Made plenty of money, too. Symptoms were transactions that had a zero "total" on the document itself, but added up in reports, transactions in non-existent periods, and the plain-text errorlog file swelling up to hundreds of MB in size when it should be more like a few hundred K. Worst one I ever got was nearly a gig. Of PLAIN TEXT. The only solutions were data repair ($700+ if yer lucky), which fixes the corruption going forward and may or may not fix the actual issue -- but it will give you a list of affected transactions that all need to be double checked...OR restore your last good backup and reenter everything by hand. Easiest one I ever did had to reenter 2 weeks worth of data. The near-GB one? Several YEARS o_O