Financial Due Diligence: The 90-Day Sprint to a Cleaner Set of Books
Financial due diligence is the buyer’s verification of whether the profit on your income statement is real, recurring, and still there after you leave. It is the point in a sale where your numbers stop being your numbers and become evidence.
Most owners get about 90 days. That is the window between a signed letter of intent and a closing date, and as of 2026 it is the honest amount of runway a lower middle-market seller has once a buyer’s analyst starts asking questions. Ninety days is enough time to organize what you already have. It is not enough time to build what you never kept.
I have watched owners spend that entire window explaining their financials instead of presenting them. Explaining is expensive. Every hour you spend reconstructing why one month looks strange is an hour the buyer spends wondering what else is strange.
How important is financial due diligence before you sell your business?
It matters more to your final price than any negotiation you will have. A buyer sets their number during the financial review, not across the table afterward, and once that number is set you are arguing against a spreadsheet instead of a person.
Here is where this review sits among the others. The legal review asks whether the buyer can actually own and operate what they are paying for. The operational review asks whether the business runs without you in the room. The financial review asks one question underneath both of them: is the money real. If the answer takes three weeks of digging to establish, the buyer does not conclude that your business is fine. They conclude that your records are unreliable, and unreliable records get priced as risk.
The output of all this work is usually a quality of earnings report, which is the document that converts your reported profit into the normalized figure a buyer will multiply. That report deserves its own treatment, and my colleague broke down how normalized EBITDA sets your multiple in detail. This piece is about the other half of the equation: what you hand the analyst, and how much of it you can fix in the time you have.
What financial documents do buyers request in due diligence?
A buyer’s financial review typically opens with a request list of eight to ten items covering the trailing three years. The list rarely varies much, which is the good news. You can build the file before anyone asks for it.
Expect to produce the following:
- Trailing 36 months of income statements and balance sheets, monthly. Annual figures hide the seasonality and the one-time events. Buyers want the monthly view because that is where the pattern lives.
- General ledger detail for the same period. This is where an analyst tests whether the summary numbers tie to actual transactions.
- Bank statements and completed reconciliations. Profit you cannot trace to a deposit is profit a buyer will discount.
- Accounts receivable and accounts payable aging schedules. Slow collections and stretched payables both tell a story about how the business really runs on cash.
- Revenue by customer, by month. This is how concentration gets measured. It is also the report most owners cannot produce quickly, and the delay itself becomes a finding.
- Payroll register and contractor classifications. Misclassified contractors are a common liability that surfaces late and costs real money.
- Tax returns reconciled to book income. When the returns and the books disagree, someone has to explain the gap, and that someone is you.
- Loan agreements, lease schedules, and any personal guarantees. These define what the buyer inherits and what has to be released at closing.
If you can hand over every item on that list in the first two weeks, you have already changed how the buyer reads your business. Preparing to pass that review is central to the work we do on the sell side, and it starts long before a letter of intent exists.
The 90-day financial due diligence checklist, week by week
Ninety days breaks into three distinct jobs, and the order matters. Trying to document add-backs before your months are closed just produces a defense of numbers that will change.
Days 1 to 30: reconcile before you explain. Close every open month. Tie every bank account to the book balance. Clear out the suspense account and anything sitting in a catch-all category waiting for your accountant to sort later. Then stop running personal expenses through the business, effective immediately, because every month of clean separation from here forward is a month you do not have to apologize for.
Days 31 to 60: build the support file. Every add-back you plan to claim needs a source document behind it, not a recollection. A one-time legal settlement needs the settlement agreement. An above-market owner salary needs a comparable. Produce the revenue-by-customer report for all 36 months, and pull the contracts that support any revenue you intend to describe as recurring. Recurring revenue without a contract behind it is just revenue that happened twice.
Days 61 to 90: pressure-test your own numbers. Hand the file to someone outside the business and ask them to read it the way a buyer’s analyst would. Take, for example, a commercial landscaping company with steady margins and one month where gross profit dropped nine points. The owner knew the reason instantly, a large equipment repair coded to the wrong account, but nobody had written it down anywhere. An analyst finding that unexplained in week two treats it as a margin problem. The same item, documented in advance with the invoice attached, is a footnote.
Most of what an outside reader flags will be small. That is the point. Small unexplained items in volume are what make a buyer slow down and widen the review.
What buyers look for in financial statements, and what makes them reprice
Buyers reprice on three things: revenue they cannot verify, earnings they cannot repeat, and cash that does not match the profit.
Revenue that cannot be traced to a contract or a bank deposit gets discounted, no matter how confident you are about it. Margin swings that nobody can explain get treated as volatility, and volatility lowers a multiple. Add-backs submitted without documentation get rejected, and here is the part that costs more than the rejected dollars: once an analyst throws out one aggressive add-back, they go back and re-examine every other one you claimed. You do not lose a line item. You lose the benefit of the doubt on all of them.
None of this requires exotic accounting. It requires records that were kept as events happened rather than reconstructed afterward. The IRS publishes plain guidance on what business records to keep and for how long, and an owner who has genuinely followed it is most of the way to a file that survives M&A financial due diligence.
The gap between book profit and collected cash gets its own scrutiny. Plenty of profitable businesses convert profit into cash slowly or unpredictably, and the financial review makes it visible. Working capital is where this surfaces at closing, through an adjustment that can move your payout in the final week.
What happens when you find the problems before the buyer does
You keep your leverage. That is the whole difference, and it is worth more than the problems themselves.
A problem you find on your own schedule is a project. You decide what to fix, how to document it, and how to present it. A problem the buyer finds is a price reduction, and it arrives at a moment when you have already told your family the deal is happening. Advisors call the practice of reviewing your own financials first sell-side due diligence, which just means you commission the same analysis a buyer would and read the findings while you still have time to act on them. The five tests worth running before you talk to a buyer are a reasonable place to start.
The timing problem is the real one. Almost everything that raises a normalized earnings figure takes longer than 90 days. Reducing customer concentration, putting recurring revenue under contract, building a management layer that operates without you, separating personal spending from business spending for long enough that the pattern is clean. None of that happens in the weeks before an analyst arrives. It happens in the years before, which is why the financial work belongs inside a broader readiness plan rather than a pre-closing scramble.
The books you hand a buyer are the first real evidence they get about how you run the business. Make them boring. Boring closes.
See what your books would tell a buyer
Clean books earn a buyer’s trust. See where yours stand and what to fix first.
