Russian to English Other Government / Politics Elections

Часть расходов могла быть по договоренности с рекламщиками проведена мимо кассы. Но доказать это почти нереально.]

My research indicates that "мимо кассы" can be a colloquial term for a failure or "screw-up," but that doesn't make sense here. It must be something like "bypassing the cash office", i.e. "off the books" or "for cash only." The расходы are Putin's election expenditure. The article alleges that (in addition to picking the opposition candidates personally, restricting their TV appearances, and no doubt preparing to fiddle the results as usual), Putin is also exceeding the maximum campaign expenditure. Well, you can't be too careful!

Can anyone confirm this sense of мимо кассы, or suggest an alternative?