How to Do Due Diligence When Buying a Business: Complete Checklist

Due diligence when buying a business is the investigation you conduct after signing a Letter of Intent but before committing to the purchase. It's your one chance to verify the seller's claims, uncover hidden problems, and decide whether the deal is worth doing at the agreed price, or at all.

Skipping due diligence, or rushing it, is one of the most common reasons buying a business goes wrong. Here's how to do it right.

For most first-time buyers, the best starting order is financial records first, legal risk review second, and operational checks third. This sequence helps you avoid spending heavily on a deal that already fails basic financial or legal tests.

What Is Due Diligence?

Due diligence is a structured review of a business's financial, legal, and operational records. The goal is to confirm that what the seller told you is true, identify risks you didn't know about, and give you the information you need to make a fully informed decision.

In most deals, the buyer has a defined due diligence period (typically 30 to 90 days) spelled out in the Letter of Intent. During this period, the seller provides access to records and the buyer investigates. In practice, 45 to 60 days is realistic for most small business transactions. Shorter timelines often lead to missed issues, while anything beyond 90 days can cause seller fatigue and deal drift.

If you discover something material during due diligence, you can renegotiate the price, add protective terms to the purchase agreement, or walk away entirely.

Financial Due Diligence

Start with the money. If the financials don't check out, nothing else matters.

Documents to Request

• Federal and state tax returns (3-5 years)
• Profit and loss statements (monthly, 3 years)
• Balance sheets (3 years)
• Bank statements (12-24 months)
• Accounts receivable aging report
• Accounts payable aging report
• Inventory list with valuations
• Equipment list with depreciation schedules
• Debt schedule (all outstanding loans, lines of credit, and obligations)

What to Look For

• Revenue trends: Is revenue growing, flat, or declining? Why?
• Customer concentration: Does 30% or more of revenue come from one customer? That's a significant risk if that customer leaves after the sale.
• Cash vs. accrual accounting: Small businesses often use cash basis, which can mask timing issues. Ask for both if available.
• Owner add-backs: Calculate Seller's Discretionary Earnings (SDE) to understand the true earning power. Be skeptical of aggressive add-backs.
• Off-books income: Some sellers claim cash income that doesn't appear on tax returns. If it's not on the return, it doesn't exist for valuation purposes. You can't verify it, and a bank won't lend against it.
• Seasonal patterns: Monthly P&L statements reveal whether the business has slow periods that require working capital reserves.

Legal Due Diligence

This is where an attorney adds the most value. Legal issues that surface after closing become your problems.

Potential liability and available remedies can vary by state law and contract language, so deal-specific legal review matters. At Surge Business Law, legal due diligence review is included in our flat-fee transaction packages, so you know the cost before you start.

Contracts and Agreements

• Customer contracts: Are they assignable? Do they have change-of-control provisions that let the customer terminate?
• Vendor and supplier agreements: Same question: will these survive the sale?
• Employment agreements: Are key employees under contract? Do they have non-competes? Are there pending disputes?
• Independent contractor agreements: Are the contractors properly classified? Misclassification creates tax liability.

Real Estate and Leases

• Lease assignment: Does the landlord need to consent to the transfer? Most commercial leases require it. Start this process early. Landlord delays can kill deals.
• Lease terms: How much time is left? What are the renewal options? A business with 6 months left on its lease and no renewal option is a different proposition than one with 5 years remaining.
• Personal guarantees: Will the landlord require you to personally guarantee the lease?

Litigation and Disputes

• Pending or threatened lawsuits
• Past settlements or judgments
• Regulatory complaints or investigations
• Customer or employee grievances

Intellectual Property

• Trademark registrations and applications
• Domain names and social media accounts
• Proprietary processes, software, or recipes
• Licensing agreements for third-party IP

Liens and Encumbrances

• UCC filings (search the Secretary of State's records)
• Tax liens (federal, state, and local)
• Judgment liens
• Equipment liens or leases

Operational Due Diligence

The numbers and legal documents tell part of the story. Operational due diligence fills in the rest.

• Key person risk: Is the business dependent on the owner or one key employee? If that person leaves, does the business still work?
• Employee retention: Talk to key employees (with the seller's permission). Will they stay after the sale?
• Systems and technology: What software, tools, and platforms does the business use? Are licenses transferable?
• Supplier relationships: Are there exclusive arrangements? Long-term contracts? Or could a supplier cut you off?
• Customer relationships: How are customers acquired? Is there a sales pipeline? What's the customer churn rate?
• Equipment condition: When was equipment last serviced? What needs replacing soon? Factor replacement costs into your price negotiation.
• Regulatory compliance: Is the business current on all required licenses, permits, and certifications?

Where Most Buyers Should Start

If you're unsure where to begin, use this order: financial records first, legal documents second, operational checks third. This sequence helps you avoid spending heavily on legal review if the financials already break the deal.

Common Due Diligence Mistakes

1. Trusting the seller's narrative without verification. Sellers are presenting the business in the best possible light. Verify everything independently.
2. Rushing the timeline. Don't let the seller pressure you into a 2-week due diligence period. 30 to 60 days is reasonable for most small business deals.
3. Only looking at financials. A profitable business with a lease that expires in 3 months or a key customer about to leave isn't as valuable as the P&L suggests.
4. Not involving professionals. Your accountant should review the financials. Your attorney should review the legal documents. The cost of professional help is a fraction of the cost of missing something.
5. Ignoring what's not provided. If the seller can't produce a document you requested, that's information too. Missing records are a red flag.

What Happens After Due Diligence?

After completing due diligence, you'll be in one of three positions:

1. Proceed as agreed: Everything checks out. Move forward to the Asset Purchase Agreement.
2. Renegotiate: You found issues that affect the value. Negotiate a price reduction, additional seller warranties, or indemnification protections.
3. Walk away: The problems are too significant or the seller won't address them. Walking away from a bad deal is always the right move.

For example, if due diligence shows a key customer can terminate after a change in ownership, you might request a price reduction, a holdback, or stronger indemnification terms before closing.

Quick Reference: Business Acquisition Checklist

Use this due diligence checklist as a starting point. Every deal is different, but these are the core items that apply to most small business acquisitions.

Financial

• Tax returns (3-5 years)
• Monthly P&L statements (3 years)
• Balance sheets
• Bank statements (12-24 months)
• AR/AP aging reports
• Debt schedule
• SDE calculation

Legal

• All customer and vendor contracts
• Lease agreement + assignment provisions
• Employment/contractor agreements
• Pending/threatened litigation
• IP registrations
• UCC and lien searches
• Licenses and permits

Operational

• Key employee interviews
• Equipment condition assessment
• Technology/software audit
• Customer acquisition and retention data
• Supplier relationship review
• Regulatory compliance verification

Get Help With Due Diligence

At Surge Business Law, due diligence support is included in our flat-fee transaction pricing. We review the legal documents, flag risks, and help you decide whether the deal makes sense before you're committed.

Book a free consultation if you're under LOI and need a risk review. Bring the seller's last three tax returns, key contracts, and lease, and we'll help you prioritize negotiation points before you commit.