How to write a business plan: sections, financials and mistakes

To write a business plan, decide who will read it, pick a format (a detailed traditional plan or a one-page lean plan), then work through the standard sections: what you sell, who buys it, how you will reach them, who runs the business and how the numbers add up. A good plan is less about polished prose and more about clear, testable assumptions. This guide follows the structure recommended by the U.S. Small Business Administration (SBA) and shows where most first drafts go wrong.

Start with the reader and the purpose

Before writing a word, answer two questions: who is this for, and what do you want them to do? A bank loan officer wants to know you can repay. An equity investor wants to know the business can grow large enough to deliver a big return. A co-founder or key hire wants to know the plan is credible. And you, the owner, need a working document that keeps decisions consistent.

The answers determine the format, the level of detail and which sections deserve the most attention.

Do the groundwork first

A business plan is only as good as the research behind it, so gather the raw material before you draft. That usually means:

• Customer evidence. Conversations with potential customers, pilot sales, pre-orders or survey results that show real demand.
• Market data. Demographic and industry information on the size and growth of your market, much of it free from government sources.
• Competitor research. Who already serves your customers, at what prices, and what they do well or badly.
• Cost quotes. Actual prices for rent, equipment, materials, insurance and professional services rather than guesses.
• Your own finances. How much you can invest, how long you can go without a salary and what collateral you have if you plan to borrow.

This research doesn’t just make the plan more convincing. It often changes the plan itself, for example by revealing that a target customer group is smaller than expected or that one supplier dominates a critical input.

Traditional plan vs lean plan

The SBA describes two main formats.

	Traditional business plan	Lean startup plan
Length	Long and detailed, with supporting documents	Typically one page
Time to write	Days or weeks	The SBA says as little as an hour
Best for	Bank loans, investors, complex businesses	Early-stage testing, internal clarity, fast-changing ideas
Focus	Full narrative plus detailed financials	Key elements only, in summary form
Updating	Periodic revisions	Frequent, as you learn

The SBA notes that traditional plans are more common and are what lenders and investors usually expect. Lean plans are less common but follow a standard structure built around nine building blocks: key partnerships, key activities, key resources, value proposition, customer relationships, channels, customer segments, cost structure and revenue streams.

Many founders start lean to test the idea and then expand into a traditional plan when they need funding.

The sections of a traditional business plan

The SBA’s traditional format has nine sections. Here is what each should do.

1. Executive summary

A brief overview of the whole plan: what the company does, the problem it solves, the target market, the team, the key financial figures and, if relevant, the funding you are seeking. Write it last, once the rest of the plan is settled, and keep it short enough to read in a few minutes.

2. Company description

Explain what the business is, the problem it solves and for whom, and the competitive advantages that will make it succeed, such as an experienced team or an ideal location. Include your legal structure. If you haven’t settled it yet, the SBA’s guide to choosing a business structure explains the trade-offs between sole proprietorships, LLCs and corporations.

3. Market analysis

Show that you understand your industry, your target customers and your competitors. Size the market realistically, describe customer needs and buying habits, and explain what competitors do well and badly. The SBA’s market research and competitive analysis guide lists useful data sources. A structured tool such as Porter’s five forces helps you explain how profitable the industry is likely to be and why.

4. Organization and management

Describe who runs the business, their relevant experience and how responsibilities are divided. An organizational chart helps. If you have advisers, a board or key hires planned, include them.

5. Service or product line

Describe what you sell, how it benefits customers and its expected life cycle. Mention intellectual property such as patents, trademarks or copyrights, and any research and development plans.

6. Marketing and sales

Explain how you will attract and keep customers and how a sale actually happens. Cover pricing, channels, promotion and the sales process. This section should connect directly to your revenue forecast: if you expect 500 customers in year one, show where they will come from.

7. Funding request

If you are raising money, state how much you need, over what period and what you will use it for. The SBA suggests explaining funding needs over the next five years. Specify whether you are seeking debt or equity and on what general terms. The SBA’s fund your business page outlines the main options.

8. Financial projections

Covered in detail below. This is where lenders and investors spend most of their time.

9. Appendix

Supporting documents: résumés, permits, licenses, letters of intent from customers, product images, credit histories and legal documents. Keep the main plan readable by moving detail here.

How to build financial projections

The SBA recommends a forward-looking financial outlook for the next five years, including forecasted income statements, balance sheets, cash flow statements and capital expenditure budgets, with quarterly or even monthly detail in the first year. If the business already operates, include historical statements for the past three to five years. If those statements are unfamiliar, our guide on how to read financial statements explains how they fit together.

Build the numbers in this order:

1. Startup costs. List one-time costs (equipment, deposits, legal fees) and monthly costs (rent, salaries, utilities). The SBA’s startup cost guide suggests counting at least a year of monthly expenses.
2. Revenue forecast. Build it from the bottom up: number of customers multiplied by average purchase multiplied by purchase frequency. Top-down estimates such as “1% of a huge market” are not convincing.
3. Operating costs. Separate fixed costs, which stay the same regardless of sales (rent, insurance), from variable costs, which rise with sales (materials, shipping, payment fees).
4. Cash flow. Profit and cash are not the same. Customers may pay late while suppliers want paying now. A monthly cash flow forecast shows when you could run short.
5. Break-even point. The level of sales at which total revenue equals total costs.

Here is a worked, hypothetical break-even example. Say a small bakery has fixed costs of $9,000 a month. Each loaf sells for $6 and costs $2.40 in ingredients and packaging, leaving a contribution margin of $3.60 per loaf. Break-even is $9,000 ÷ $3.60 = 2,500 loaves a month, or roughly 83 a day over 30 days. That single number tells the owner, and a lender, whether the plan is realistic given the shop’s size and foot traffic.

Finally, list your key assumptions in one place: prices, conversion rates, growth rates, payment terms, hiring dates. Readers trust projections more when they can see and challenge the logic.

Common business plan mistakes

• Hockey-stick revenue with no explanation. Sharp growth is possible, but every jump needs a cause: a new channel, a new product, more salespeople.
• Ignoring cash flow. Profitable businesses still fail when they run out of cash. Show the monthly cash position for the first year.
• “We have no competitors.” Every business has competition, even if it is a substitute or the customer doing nothing. Claiming otherwise undermines credibility.
• A vague target market. “Everyone” is not a market. Define specific customer segments you can actually reach.
• Inconsistent numbers. Hiring plans, marketing budgets and revenue forecasts must agree across sections.
• Too much jargon, too little evidence. Replace adjectives with data, customer quotes you’ve genuinely collected, or pilot results.
• Writing it once and filing it away. Compare results with the plan each quarter and update it when reality diverges.

The bottom line

Learning how to write a business plan is really learning to think clearly about a business: who it serves, why they will pay, what it costs and how much money it needs. Choose the format that fits your reader, follow the standard sections, and make your financial projections traceable to stated assumptions. A plan that is honest about risks is more persuasive than one that pretends there are none. For more on strategy and planning, see our guide to corporate strategy and the rest of our Business & Strategy hub.