Every garage owner I talk to says the same thing about their operator's numbers

Both things are happening. Transient cash is the historically leaky part of the business and that's exactly why the standard agreements have audit language, so an owner without it made a choice, usually by signing the operator's form.

What the fix looks like in practice depends on the equipment. If the garage runs a modern PARCS with license plate recognition at entry and exit, you can reconcile at the transaction level: every entry event should terminate in a paid exit, a validated exit, a monthly credential, or an exception the operator has to explain. Exception rate is the number you watch. If the garage still runs sequential tickets, you audit the ticket stock, and unaccounted ticket numbers are where you look. Either way you want the raw transaction export delivered to you directly by the equipment vendor, not filtered through the operator's monthly statement. That single provision does more than an annual audit.

On cost, revenue audit firms typically bill hourly or on a per-facility engagement, and mystery shopping is usually a modest per-visit fee. Owners with a few facilities tend to buy it once, find or not find something, then move to continuous data feeds because they're cheaper than repeat engagements.

A minimum annual guarantee lease looks like it solves this and mostly moves the problem. You've now got a percentage rent over a breakpoint, and percentage rent is reported by the same party you didn't trust. You still need reporting and audit rights, plus a right to inspect during the term and a lookback window after it ends.

The piece owners underweight is that the operator often also holds the merchant account. If the card money lands in the operator's account first, your recourse in a dispute is a lawsuit rather than a bank instruction. Put the deposits in the owner's account and let the operator draw fees.

The merchant account point reframes the whole thread for me. That's not an audit problem, it's a question of whose hands the money passes through first, and it's fixable at signing for free.

Dumb question I'd rather ask here: what counts as an exception in that reconciliation? If someone loses a ticket and pays a lost ticket fee, is that an exception or a normal paid exit?

Lost ticket fees are a normal paid exit in most systems, compass, but the rate at which they occur is itself a tell. If one cashier's shift produces triple the lost ticket transactions of everyone else's, that's the flag. Plumb, that's probably where your service niche actually is, shift-level pattern reporting that no owner with two garages is going to build themselves.

Owners will pay for this right after they've been burned and not one day before. I'd sell it as monthly reporting bundled at a few hundred a facility rather than a $9,000 audit engagement, because the audit is a purchase and the report is a habit.

The lookback window is the clause I'd argue hardest over. Most operator forms give you 90 days to object to a statement, after which it's deemed accepted, and a skim you find in year three is then unrecoverable by contract. I'd push for 24 months and a provision that the operator pays audit costs if the variance exceeds some threshold, say 3%. Whether a deemed-accepted clause is enforceable as written depends on state contract law, so that's an attorney question, but nobody should be signing 90 days without noticing it.

Adding audit rights and deposit control to my list of things to check on every parking listing I look at, alongside the redevelopment termination clause from verity's thread. Two clauses, and both of them are free at signing and expensive later.