Why Deals Fall Apart in Diligence: The Five Recurring Killers

After a hundred-plus lower middle market transactions, the reasons deals die in diligence are remarkably consistent.

Roughly one in three signed LOIs in the lower middle market doesn't make it to close. The reasons cluster tightly. If you can spot them before signing, you save the diligence spend and, more importantly, the time.

The five killers

• Customer concentration surfaces late. The CIM shows a diversified customer base. The QofE reveals customer #1 is 34% of revenue and hasn't renewed a contract in eighteen months.
• Seller can't produce clean financials. Tax returns don't tie to internal P&Ls. AR aging doesn't reconcile. No monthly close discipline. This isn't a diligence problem — it's a business problem the seller didn't disclose.
• Key-person risk crystallizes. The sales manager who owns half the customer relationships tells the buyer, on a site visit, that he's not staying past the transition. Deal value drops 25% overnight.
• Environmental or regulatory issue. A Phase I turns up something. A licensing issue turns up something. Neither is fatal, but both restart the clock — and often the negotiation.
• Working capital delivery gap. The seller can't deliver the peg without either injecting cash or delaying close. Either signals a problem that changes the underwriting.

What buyers should do differently

• Ask for the customer concentration cut *before* LOI, not after.
• Insist on trailing-twelve monthly financials with a full reconciliation to tax returns before signing.
• Interview at least two non-owner key employees before final LOI.
• Order environmental and licensing checks in parallel with QofE, not after.
• Set the working capital peg on a trailing-twelve average with adjustment mechanics defined in writing.

None of it is exotic. All of it is skipped, routinely, and it's the reason the deal-mortality rate is what it is.