That is a cool idea because the spreadsheets are probably not backed up so you have no reference to compare it to. This is not exactly the case in the markets.

That is a cool idea because the spreadsheets are probably not backed up so you have no reference to compare it to. This is not exactly the case in the markets. For instance when I send my order into NASDAQ, I get an order accept message back that includes all the parameters in the original order message. If you artificially cancel my order when I think the order should have executed immediately or been posted to the book, I'll notice that and call the exchange trade desk to ask wtf happened. For displayed, non-IOC orders I'll also see my order in the market data feed. When I get an execution the price of the execution should match (or improve) the price of my order. I'll also see copies of all these orders and executions in the DROP copy from my clearing firm. In other words there are a lot of places to insert your own surveillance to make sure your trading is happening the way you expect it to, and many firms already have such surveillance schemes in place because 1) regulatory requirements and 2) software has bugs and sometimes things break. * This is all re US equity markets because that's my area of expertise. Maybe it's different on other electronic venues.