> A few presidents ago, the chairman of the joint chiefs publicly said that 7 trillion in military spending is unaccounted for.

You're likely referring to the fact that the pentagon can't pass an audit even though there have been requirements going back to the 90s. That's more about tracking where the money they spent is going as opposed to the total quantity of money they are spending though, i.e. the $800bn is "accurate" but some portion of it may have vanished due to bad accounting, corruption, waste, fraud, etc...

Having said that any accounting for an entity the size of the US government is non-trivial. The numbers I stated above are not the final numbers. Firstly because it's YTD but also because of the complexity in the accounting. We have decades of trend lines and a lot of public data on tax receipts, bond auctions, and the like to know that defense spending isn't drastically different than what is being reported though. If you have any analysis that concludes otherwise I would enjoy reading it.