Buyer's Guide · Buying a business
Due diligence before buying a business
Due diligence is the verification window between agreeing on a price and actually buying. It's your chance to confirm the seller's claims against source documents and to check everything that isn't financial (the lease, the licenses, the condition, the legal exposure). It runs for a fixed period after the Letter of Intent, typically 30 to 60 days, and it's the last point at which you can walk away without losing your deposit. Skip it, rush it, or trust the seller's spreadsheet instead of the source documents, and you inherit every problem you didn't find.
When you agree to buy a business, you don't hand over the money that day. You sign a Letter of Intent (LOI), which opens a due-diligence period: a window where you get access to the real records and verify that the business is what the seller said it is. Everything you don't catch in that window becomes your problem the day you close.
Due diligence splits into four areas. Most first-time buyers fixate on the financials and forget that a profitable business is worthless if the lease can't transfer or the licenses don't move to you. Here's how to cover all four areas without missing the one that sinks the deal.
The four areas of due diligence
1. Financial: can you prove the numbers?
Get the last three years of federal tax returns, the full P&L statements, and the business bank statements, not the seller's one-page summary. Recalculate the real owner earnings (SDE) yourself and tie the revenue on the P&L to the tax returns and the bank deposits. Tax returns are the anchor: a seller inflates a spreadsheet far more readily than the figures they filed with the IRS.
How to read a P&L when buying a business2. Legal: does everything transfer to you?
Confirm the lease term and whether it's assignable, that every license and permit can move to a new owner, and run a search for liens, judgments, and pending litigation. A business that runs beautifully is worthless if the landlord won't approve the transfer or a key license is non-transferable.
3. Operational: what happens when the seller leaves?
Understand who actually runs the business day to day. If the owner is the business (the relationships, the know-how, the hours behind the counter), then the earnings walk out the door with them unless you budget for replacement labor or a real transition period. Confirm supplier terms, employee roles, and any customer concentration.
4. Physical & environmental: what are you inheriting?
Inspect the equipment, the facility, and (where relevant) the environmental exposure: underground tanks, health-code compliance, deferred maintenance. These don't show up on a P&L, and they can cost more than the business itself. A paper review can't replace an on-site inspection.
The full due-diligence checklist
The documents to demand
- Three years of federal tax returns (the anchor, filed under penalty of perjury)
- Full profit-and-loss statements and the business bank statements
- The lease, with all amendments, renewal options, and the assignment clause
- Every license and permit, plus written confirmation each can transfer
- Any franchise agreement, with remaining term and transfer-approval process
- Supplier and vendor contracts, the equipment list, and the employee roster
Buying a specific business type? Start from the vertical checklist: gas stations or convenience stores.
The timeline and the cheapest “no”
Due diligence runs inside a fixed window after the LOI, usually 30 to 60 days. Spend it in the right order: catch the deal-breakers with a cheap first pass before you spend on the expensive professionals, not after.
| A first-pass document check (Quick Scan) | $49 |
|---|---|
| A deal attorney | ~$5,000 |
| An accountant / quality-of-earnings review | ~$3,000+ |
| A full due-diligence firm | ~$15,000 over two weeks |
| Discovering the problem after you've closed | Your investment |
The mistakes that wreck deals
- Trusting the seller's spreadsheet instead of the tax returns and bank statements.
- Doing financial due diligence and skipping the lease, licenses, and physical condition.
- Signing an LOI with no due-diligence period, or one too short to get franchisor/landlord approvals.
- Staying in a deal because you've already sunk time and money into it. The cheapest “no” is the early one.
What due diligence can't tell you
Even a thorough review can't assess physical condition you haven't inspected, employee morale, undisclosed litigation, real-time market shifts, or the seller's true motivation. Verify everything that's verifiable on paper, then cover the rest with an on-site visit, your attorney, your accountant, and direct questions to the seller.
Start your due diligence in minutes
Upload the seller's P&L, tax returns, and bank statements, and BizScore computes the real SDE, ties the revenue to the returns, and flags every red flag, each backed by the exact document it came from. The fastest, cheapest first pass before you spend on a lawyer.
Frequently asked
- What is due diligence when buying a business?
- It's the verification window between agreeing on a price and closing, usually 30 to 60 days after the Letter of Intent, where you confirm the seller's claims against source documents and check everything non-financial (lease, licenses, condition, legal exposure). It's your last chance to walk away without losing your deposit.
- How long does due diligence take?
- Typically 30 to 60 days, negotiated into the Letter of Intent. Build in enough time for slow-moving approvals: a franchisor transfer or a landlord's lease-assignment consent can each take weeks on their own.
- What documents should I ask for during due diligence?
- At minimum: three years of federal tax returns, full P&L statements, and business bank statements; the lease with its assignment clause; every license and permit with transfer confirmation; any franchise agreement; and supplier contracts, the equipment list, and the employee roster.
- Can I do due diligence myself or do I need professionals?
- Both. A first-pass document check tells you whether a deal is even worth professional fees. Then a deal attorney and an accountant verify the legal and financial details before you sign. The order matters: a cheap early check saves you from paying thousands to confirm a deal you should have walked away from.
About this guide
BizScore is built by first-time business buyers — people who watched someone close to them lose their life savings on a deal that looked clean on a spreadsheet and fell apart in the documents the seller never volunteered. That experience is why these guides exist, and why every BizScore report cites the exact document behind each finding.
Where the numbers come from: the benchmark ranges in our guides — SDE multiples, expense ratios, typical timelines — are widely-used industry rules of thumb, cross-checked against the analytical benchmarks BizScore applies inside its reports. Dollar figures such as a ~$15,000 quality-of-earnings review or a $5,000 deal attorney are representative of what buyers typically pay, not quotes; actual costs and multiples vary by deal. We review these figures periodically — last updated June 2026.
BizScore is an information service — think of it as a Carfax for a small business — not a CPA, an attorney, or financial advice. Use it to decide where to spend your professional dollars, and bring in a qualified professional before you sign anything.
This guide is general education, not legal, financial, or tax advice. Every deal is different. Verify against the actual documents and talk to a qualified professional before you sign anything.