How to Research a Stock: From Business Model to Investment Decision

What should you research before buying a stock?

Before buying a stock, investigate its business model, financial statements, competitive position, valuation and risks. Then assess whether the investment fits your holding period and existing portfolio. No single ratio answers all of these questions.

Use the following questions to keep the investigation focused:

The evidence column matters. “Strong company” is a judgement; it needs a reason you can check.

Where can you find reliable information about a stock?

Start with regulatory filings and the company's investor-relations website. For many US reporting companies, the annual Form 10-K, quarterly Form 10-Q and material-event Form 8-K provide the foundation. Broker research, screeners and AI summaries can help you navigate information, but important claims should be checked against the underlying source.

The SEC's EDGAR database provides public filings. Investor.gov explains that a 10-K contains audited annual financial statements and risk disclosures; a 10-Q provides unaudited quarterly statements and updates. An 8-K reports material events between scheduled reports. Some issuers use different forms, including foreign private issuers.

Record the document, reporting period and location of each important figure. A number copied from an undated screenshot is difficult to verify later.

Management presentations are useful for understanding management's argument. Read them alongside the financial statements and disclosures, rather than treating the presentation as independent confirmation.

Step 1: Explain the business before looking at the valuation

Write a short explanation of how the company makes money:

The company sells ___ to ___. Customers choose it because ___. Its largest costs are ___. The main threat to its revenue is ___.

If you cannot complete that explanation, you have an information gap.

Then identify what drives changes in revenue. Is the company selling more units, raising prices, buying other businesses or benefiting from exchange-rate movements? These explanations imply different expectations for future growth.

For a subscription business, you might investigate customer retention, pricing and the cost of winning new customers. For a manufacturer, capacity, input costs and capital expenditure may be more relevant. Choose measures that explain the business rather than collecting every available ratio.

The SEC's guide to reading a 10-K identifies the business description, risk factors, management discussion, financial statements and accompanying notes as useful starting points.

Step 2: Read the financial statements together

Use the income statement to examine revenue and profit, the balance sheet to examine assets and obligations, and the cash-flow statement to examine cash movements. Also check the statement of shareholders' equity and the notes, particularly where share issuance or accounting treatment matters.

A useful research question is: do the statements tell a consistent story?

For example, if revenue and profit are growing but operating cash flow is weakening, investigate the difference. It might reflect investment in working capital, customer payment timing or another disclosed cause. The mismatch is a reason to investigate, not automatic proof of wrongdoing.

Compare several reporting periods and use consistent definitions. Do not compare one company's adjusted profit with another company's reported profit without examining the adjustments.

For each apparent improvement, ask:

• What changed operationally?
• Is the improvement recurring or temporary?
• Does it improve the economics for each shareholder?

That final question prevents company growth from being confused with growth in the value attributable to an individual share.

Step 3: Check cash generation and financing risk

A commonly used free-cash-flow calculation is:

Free cash flow = cash flow from operations − capital expenditure.

Definitions vary, so identify the exact figures used and keep the calculation consistent across periods. Free cash flow is different from accounting profit and should be assessed alongside it.

Ask why cash flow changed. A temporary reduction during a disclosed investment programme may deserve a different interpretation from a continuing shortfall caused by weaker trading.

For financing, examine cash balances, borrowings, maturity dates, interest obligations and any disclosed restrictions. Avoid declaring a business safe solely because its cash balance looks large. Compare available resources with the obligations and operating needs they must cover.

Record how additional funding would affect shareholders if it became necessary. Treat that as a scenario to examine, not a prediction that the company will raise money.

Step 4: Separate business quality from the price you pay

Valuation asks how the price relates to the business's financial performance and prospects. The price-to-earnings ratio compares share price with earnings per share; other measures examine cash flow, assets or enterprise value. Ratios are useful comparisons, but their interpretation depends on the business and the numbers behind them.

For this workflow, make two separate statements:

1. 1.Business assessment: what appears strong or weak, supported by evidence.
2. 2.Price assessment: what assumptions are needed to justify the purchase price.

This separation stops a favourable business description from substituting for a valuation argument.

Compare like with like. If one business has different growth, financing or investment requirements, an apparent valuation discount may need an explanation. Do not assume every discount is a mispricing.

How can you judge whether a stock's price is reasonable?

Estimate a range using explicit assumptions about future per-share performance and valuation, then compare that range with the purchase price. Test less favourable assumptions as well as your preferred outcome. The result is conditional on the inputs; it is not an objectively certain price target.

Here is a simplified example using a fictional company, Harbour Components. All figures and scenarios are invented for education. Currency is US dollars; each financial figure represents a hypothetical full year unless stated otherwise.

The starting calculations are:

• Market capitalisation: $30 × 100 million = $3 billion.
• Earnings per share: $150 million ÷ 100 million = $1.50.
• Price-to-earnings ratio: $30 ÷ $1.50 = 20.
• Free cash flow under the stated definition: $190 million − $70 million = $120 million.

These calculations describe the hypothetical starting point. They do not establish that $30 is attractive.

Now specify three possible outcomes at the end of a three-year holding period:

Calculation: ending price = $1.50 × (1 + assumed EPS growth)³ × assumed ending P/E. Prices and returns use unrounded inputs; displayed EPS is rounded. Returns are cumulative price changes over three years, not annual returns, and exclude dividends, fees, taxes and inflation.

The middle scenario produces earnings growth, yet only a modest price gain because the assumed valuation multiple falls. Business growth alone does not settle the investment question.

None of the growth rates or ending multiples is justified merely because it appears in this table. In real research, connect those assumptions to operating evidence, financing, share-count changes and relevant comparisons. This simplified model assumes positive earnings and an EPS-based valuation; it is unsuitable as a standalone approach for many loss-making businesses.

Do not describe the middle scenario as “most likely” without evidence. This example assigns no probabilities and therefore makes no expected-return claim. Discounted cash flow is another valuation approach, but it also depends on assumptions about future cash flows and discount rates.

Step 5: Write the strongest case against your conclusion

Before deciding, list the developments that would weaken the argument.

For Harbour Components, those might include customers buying less, costs rising faster than prices, or future share issuance reducing per-share earnings. These are hypothetical research questions, not established facts about a real company.

Use a simple evidence table:

An empty contrary-evidence column is a prompt to investigate further. Do not fill it with token objections that leave the original argument untouched.

Step 6: Make a decision you can review

Your research should support one of three outcomes: proceed within your portfolio constraints, keep the stock under observation, or reject the idea. Insufficient evidence is a valid reason to defer.

Record the decision in a short research note:

Keep the original note when updating the research. That makes it possible to see whether the evidence changed or whether you changed the story after the price moved.

Is a low P/E ratio enough to decide that a stock is cheap?

No. A low P/E ratio shows a low price relative to the earnings figure used. It does not establish that those earnings are sustainable or that the business deserves a higher valuation. Check the reporting period, one-off items, financial condition and future assumptions before treating a low ratio as an opportunity.

Can AI do the stock research for you?

AI can assist with organising documents, extracting questions and preparing draft comparisons. Treat its output as material to verify. Check important figures against filings, recalculate numerical examples and separate sourced facts from generated interpretation.

For each consequential AI-generated claim, ask: what is the source, what period does it cover, and does the evidence support the conclusion? If those questions cannot be answered, do not use the claim to support the decision.

Stock research checklist

Before considering the research complete, confirm that you can:

• Explain how the business makes money without repeating its marketing language.
• Locate the relevant filings and identify the reporting periods used.
• Explain the relationship between profit, cash flow and financing needs.
• Distinguish company growth from per-share performance.
• State the assumptions behind the valuation and test a less favourable outcome.
• Identify meaningful contrary evidence and remaining information gaps.
• Explain the holding period and portfolio exposure being considered.
• Record a decision and the evidence that would make you reconsider it.

If a missing answer could materially change the decision, investigate it before treating the research as complete. The purpose of the process is a judgement you can explain, verify and revise.