How to Do Startup Due Diligence in One Hour

The honest truth about angel and small-fund due diligence is that most decisions worth spending 30 hours on could have been made with equal quality in 60 focused minutes. The remaining 29 hours are usually confirmation work, not decision work. This is not a claim that diligence does not matter. It is a claim that most diligence time is poorly allocated.

If you are writing small checks in early-stage rounds, where full formal diligence is neither economically feasible nor particularly predictive, you need a different tool. Not a shortcut. A framework that concentrates the diligence where it is actually decisive, and skips the parts that do not change the answer.

This is the one-hour due diligence framework I use for small checks. It is structured, defensible, and repeatable. It will not make every investment a winner. No diligence can. What it does is make sure your yes and no decisions are based on the inputs that actually matter at early stage.

What the One Hour Is For

Before the structure, the scope.

This framework is for angel and small-fund checks at pre-seed or seed, where your investment size makes full formal diligence disproportionate to the risk. Typically, checks from $5K to $50K into companies valued at $3M to $30M post-money.

For larger checks (hundreds of thousands or more) or later-stage rounds (where financial diligence, customer diligence, and technical diligence genuinely matter), you need something more comprehensive.

The full due diligence guide → covers the comprehensive version. This post is the right-sized version for small checks.

The Six 10-Minute Blocks

The hour splits into six focused blocks. Each block has a clear deliverable.

Block 1: Deck Review (10 minutes)

Read the deck carefully but once. Write down three things by the end:

• The three things that make you believe.
• The three things that worry you.
• The one thing you most want to verify or understand better.

Do not research anything during this block. Just read, think, and write.

The output of this block is a structured view of your initial read, which will anchor the rest of the diligence. Skipping it leads to diligence that drifts toward confirming whatever your first impression was, without you noticing.

Block 2: Market and Competition (10 minutes)

Open a few browser tabs. Answer:

• Who are the three most obvious competitors or substitutes for this company?
• How is this company meaningfully different?
• What is the realistic size of the market if this company succeeds?
• Why now? What has changed in the last two to five years that makes this possible?

You are not writing a McKinsey report. You are sanity-checking whether the market story holds up to 10 minutes of outside investigation. Most failed early investments fail here. The market was wrong, too small, or too crowded, and the investor did not check.

Block 3: Team Background Check (10 minutes)

LinkedIn and Google for each founder. Specifically:

• What have they done before, and how does it connect to this problem?
• Is there anything in their history that raises concerns (brief tenures, unexplained gaps, concerning exits)?
• Can you find their writing, talks, or previous work that demonstrates the depth they claim?
• What does their public presence suggest about how they operate (substantive, shallow, ego-driven, builder-focused)?

This block will not tell you whether the founders are excellent. It will tell you whether they are plausible. At early stage, plausibility is usually enough to justify moving forward. Obvious red flags here (poor track record, evasive background, clear misalignment with the problem) are often enough to justify a pass.

Block 4: Traction Review (10 minutes)

If there are any numbers in the deck, stress-test them.

• What is the base these numbers are computed against? Is the growth rate off a trivial base?
• Is retention included, or only acquisition? Retention is the harder number.
• Are these numbers consistent with what you can observe externally (web traffic patterns, app rankings, hiring scale)?
• What is the most concerning single data point, and how does the founder explain it?

Founders curate their traction slides. That is expected. Your job is to separate the curated view from the underlying reality. If the underlying reality is weaker than the pitch, this block is where you notice.

For pre-revenue companies, substitute: what qualitative signals of product-market fit exist, and how strong are they.

Block 5: Terms and Fit (10 minutes)

The mechanics. Write down:

• Stage, round size, valuation (pre-money and post-money).
• Instrument type (SAFE, note, priced) and key terms.
• How does the valuation compare to comparable deals in the sector?
• Does this fit my thesis? Stage, sector, geography, check size.
• At what exit outcome does this become a good investment at this entry price?

If any of these answers are uncomfortable, this block is where you see it. A valuation 50% above comparable sector deals needs a specific reason. A deal that does not fit your thesis needs a specific exception to justify. An entry price that requires a near-perfect exit to return anything should trigger caution.

Valuation methods → get explored in more depth elsewhere. For a one-hour framework, the comparison to market comparables is the practical test.

Block 6: Gut Check and Decision (10 minutes)

Pull it all together. Answer three questions, writing down actual words:

1. Why would I invest? The specific, honest reasons. Not "because it is a great opportunity." Specific reasons grounded in what you just learned.
2. Why would I pass? The specific concerns that justify a no. Honest version, not pro-forma.
3. What outcome would change my answer? If you are leaning yes, what new information would push you to no? If leaning no, what would push you to yes?

Then decide. Yes, no, or "need one specific additional data point" (with the data point specified).

If you cannot reach a decision after a focused hour, the problem is usually either a missing data point (which you name explicitly and pursue) or a fundamental fuzziness that more time will not fix. Both are actionable.

What to Skip

The framework works because it skips specific things that do not inform the decision at small-check scale.

Skip: Detailed Financial Models

At pre-seed and seed, financial projections are fiction. Validating them does not change your answer. Note whether the financial reasoning is coherent and move on.

Skip: Detailed Technical Architecture

Unless you are a technical specialist and this is a technical bet, the architecture diagram is not a diligence-decisive input at your check size.

Skip: Reference Checks on the Founder

Controversial take. Reference checks are extremely valuable. They also take hours if done well. For small checks, you can do them later if the deal advances, or skip them if the rest of the diligence and your own founder impression is strong enough.

If your check is substantial or the decision is close, add reference checks as a Block 7. For the core hour, they are outside scope.

Skip: Detailed Customer Calls

Same logic as reference checks. Valuable, but expensive in time. Do them if the decision is close after the one-hour framework. Skip them if the decision is already clear.

Skip: Competitive Deep Dives

A 10-minute competitive scan is enough for a first decision. If you want to invest, a deeper competitive analysis can happen between first decision and wire. It does not need to happen in the first hour.

When the One-Hour Framework Is Not Enough

Honestly, it is not always sufficient. A few situations where you should extend diligence before committing.

Large Check by Your Standards

If this check is materially larger than your typical check, extend. A 3x-your-normal check deserves 3x-your-normal diligence.

High-Risk Sectors

Regulated industries, hardware companies, deep tech, biotech. These sectors have specific diligence requirements that the one-hour framework cannot cover.

Close Calls

If after the hour you are 51/49, extend. Close calls are where additional diligence can actually change the answer. Clear calls benefit less from additional time.

First Check From a New Sponsor or Lead

If you are investing alongside a lead or sponsor you do not know, extend. Some of the "diligence" you are effectively outsourcing to them needs to be re-checked when the relationship is new.

Something Specifically Surprised You

If any of the six blocks surfaced something you did not expect, that surprise deserves its own follow-up. Surprises are data.

How This Gets Faster Over Time

The framework is rigid for your first 10 to 20 applications of it. After that, pattern recognition compounds and the six blocks become faster.

Experienced investors can often run this entire framework in 30 minutes because they have internalized what to look for in each block. Red flags and green flags are recognized faster. Market comparisons draw on accumulated knowledge. Team evaluation becomes calibrated.

The first 20 applications are tuition. The next 200 are compounding.

The Single Most Important Habit

Regardless of the framework, one habit matters more than any other: writing down your reasoning at decision time.

Before every check, write one paragraph (not one sentence, one actual paragraph) explaining why you invested and what you expect to happen. Save it somewhere you will find it later. Re-read it quarterly for the first two years of the investment's life.

This is the single most valuable practice I know for improving your own judgment over time. The gap between what you thought would happen and what actually happened is where your real learning lives. Without the written record, that learning evaporates into generalized "I was kind of bullish" memory that teaches you almost nothing.

The Process vs. the Output

A final point worth internalizing.

Due diligence does not guarantee outcomes. Excellent diligence sometimes precedes investments that fail. Sloppy diligence sometimes precedes investments that win. The variance at early stage is enormous, and no diligence framework eliminates it.

What diligence does is give you a defensible, repeatable process. Over 50 to 100 investments, a rigorous process produces better average outcomes than a sloppy one. But on any given investment, the outcome is driven by forces well outside your diligence quality: market shifts, competitive entrants, founder decisions you had no way to predict, macro conditions.

The one-hour framework is not about being right about any specific deal. It is about being systematic across many deals. That systematic quality is what compounds over a career.

Angels and small-fund managers who skip structured diligence entirely produce scattered outcomes. Angels and small-fund managers who do the hour-long framework consistently produce better aggregate returns, even though any specific investment can still surprise them.

Use the framework. Write the memos. Review them over time. That is the whole practice.

If you want an intelligence platform that makes blocks 2 through 5 of the framework faster (real-time sector data, valuation comparables, company backgrounds, and signal-based intelligence →), that is what Brevoir → is built for. The one-hour framework is faster when the market intelligence layer is already populated. Structured diligence at the speed the market actually moves.