How Much Should You Budget for Due Diligence? A Deal-by-Deal Breakdown

Buyers routinely under-budget for due diligence and get surprised at closing. Here's what each professional actually costs — and how to size your budget before you sign an LOI.

Why Buyers Underestimate This Cost

The due diligence budget is easy to ignore during the excitement of finding a good deal. Buyers focus on the down payment, the loan terms, and the business's financials — and treat professional fees as a footnote.

The problem: those fees are non-refundable. If the deal falls through after you've ordered a quality of earnings report and paid your attorney for two weeks of document review, you're out that money regardless. The due diligence budget is therefore not just a cost — it's a risk you're taking on the moment you sign an LOI and begin exclusivity.

Sizing it correctly upfront protects you from two bad outcomes: underspending (and missing something that costs you far more post-close) and overspending (running up professional fees on a deal that should have been walked away from sooner).

What Due Diligence Actually Costs: The Full Breakdown

Budget 1–3% of the purchase price for due diligence. A $500K deal: $5,000–$15,000. A $2M deal: $20,000–$60,000. The percentage shrinks as deal size grows — fixed costs like attorney fees don't scale linearly with price.

The Most Important Line Item: Quality of Earnings

A Quality of Earnings (QoE) report is a third-party financial analysis of the target business, performed by an independent accounting firm. It goes deeper than a standard CPA review — it reconstructs the income statement from source documents (bank statements, invoices, contracts), validates every add-back the seller claims, identifies revenue trends at the customer level, and flags accounting irregularities.

For deals under $500K with straightforward financials, a QoE may be overkill — your CPA can handle the financial review. For anything above $1M, or any deal where the seller's financials seem unusually clean or the add-backs feel aggressive, a QoE is worth every dollar.

What a QoE will find that a basic review won't:

- Revenue pulled forward from future periods to inflate the trailing twelve months

- Customer churn not visible in annual revenue totals

- Expenses cut in the months before sale to inflate margins temporarily

- Add-backs that are actually recurring costs mislabeled as one-time

- Working capital requirements that weren't disclosed

A QoE that surfaces a $50,000 revenue discrepancy on a $1M deal just saved you $150,000–$300,000 in purchase price — or got you out of a bad deal entirely.

Attorney Fees: What You're Actually Paying For

Your transaction attorney handles the legal side of the acquisition: reviewing the purchase agreement, negotiating representations and warranties, drafting the seller note (if applicable), reviewing lease assignments, employment agreements, and non-competes, and coordinating the closing.

Fee structures vary:

Hourly billing: Most common. Expect $350–$700/hour for a mid-market M&A attorney at a regional firm. A straightforward asset purchase with a cooperative seller might run 15–25 hours. A complex deal with multiple issues can hit 50+ hours.

Flat fee: Some attorneys offer flat fees for standard small business acquisitions — typically $5,000–$12,000. This works well when the deal is clean. If complications arise, they'll often convert to hourly or add a premium.

What drives the bill up: Sellers who change terms after LOI, landlords who resist lease assignments, employment issues uncovered during diligence, lender document requirements, and last-minute renegotiations.

Do not try to save money by using a general-practice attorney or a family friend who dabbles in business law. A specialist who does these deals weekly will cost less in total than a generalist who takes twice as long and misses standard protections.

Deals Where Diligence Costs More

Real estate included: Add a commercial appraisal, title search, environmental review, and extra attorney time. Budget an additional $5,000–$10,000.

Healthcare businesses: HIPAA compliance review, billing audit, licensing verification, and credentialing analysis can add $5,000–$15,000 in specialist fees.

Franchise acquisitions: Franchise disclosure document (FDD) review by a franchise attorney ($1,500–$4,000), plus franchisor transfer approval process which can take 30–60 days and sometimes includes transfer fees of $5,000–$25,000 paid to the franchisor.

Businesses with employees in multiple states: Multi-state employment law review adds complexity and cost.

Businesses with pending litigation: Your attorney will need to assess exposure and may involve a litigation specialist. Budget unpredictably here — it depends on what you find.

How to Control Diligence Costs Without Cutting Corners

• ›Get a scope estimate before engaging anyone. Ask your attorney and CPA for a scoping call before you sign an engagement letter. Walk them through the deal size, industry, and complexity. A good advisor will tell you upfront what the likely fee range is.
• ›Do your own first pass. Before handing anything to professionals, review the last three years of tax returns and bank statements yourself. Build your own SDE model. Come to your CPA with a list of questions, not a blank slate — you'll save hours of billable time.
• ›Sequence your diligence. Start with the highest-risk items for your specific deal. If revenue concentration is your biggest concern, get customer-level data and call references before ordering a full QoE. If you find a dealbreaker early, you've saved the cost of everything that would have come after.
• ›Set a kill fee threshold. Decide in advance at what point you'll walk away if a problem is found — and what finding would trigger that. Having this decision made before you're emotionally invested in the deal makes it easier to act rationally.
• ›Negotiate the purchase price adjustment before, not after. If diligence surfaces an issue, you can either renegotiate or walk. Walking mid-diligence still costs you what you've spent so far. A well-structured LOI with a "material adverse change" clause gives you legal grounds to exit without penalty.
• ›Don't skip the cheap stuff. UCC lien searches ($200) and background checks ($300) are the highest ROI items on this list. A lien on business equipment or a seller with undisclosed legal history can kill a deal that would have closed otherwise.

What Happens If You Skip Diligence

Skipping or shortcutting due diligence doesn't eliminate the risk — it defers it to post-close, where the cost is catastrophically higher.

A buyer who skips a QoE and misses $80,000 in inflated add-backs has effectively overpaid by $240,000–$320,000 (at a 3-4x multiple) — and there's no recourse once the deal closes unless fraud can be proven.

A buyer who doesn't do an IT audit inherits software licenses that can't be transferred, discovers the "proprietary system" was built by a contractor who owns the code, or faces a ransomware event on infrastructure the seller knew was exposed.

A buyer who doesn't verify the lease terms discovers the landlord won't extend beyond the remaining 14 months — and the whole premise of the deal was a 10-year location.

These aren't hypotheticals. They're the stories acquisition attorneys and business brokers tell about deals gone wrong. The cost of diligence is certain and bounded. The cost of skipping it is uncertain and potentially unbounded.

Budget by Deal Size: Quick Reference

One More Thing: Budget for the Deal That Doesn't Close

Experienced acquirers know that not every deal under LOI makes it to close. The industry average is that roughly 30–50% of deals in diligence fall apart before closing — due to financial discrepancies, seller cold feet, lender issues, or undisclosed liabilities.

This means your diligence budget isn't just for the deal you close. It's across all the deals you seriously pursue. A buyer who looks at three deals seriously before closing one should budget diligence costs for three — even if they walk from two of them.

Factor $5,000–$15,000 per serious deal attempt into your overall acquisition budget. It's the cost of doing the work correctly, and it's far cheaper than closing a deal you shouldn't have.