The Startup Due Diligence Checklist Every Angel Investor Needs

Here is an uncomfortable truth about angel investing: the majority of angels who lose money do not lose it because they picked the wrong markets or backed the wrong technologies. They lose it because they did not do the work. They heard a compelling pitch, liked the founder, got excited about the vision, and wrote a check without ever opening the hood.

Due diligence is not glamorous. It is not the exhilarating part of angel investing. It is phone calls with customer references who may not call you back. It is reading through operating agreements and cap tables looking for red flags. It is running financial models that force you to confront whether the company's growth assumptions are remotely plausible.

It is also the single most important skill an angel investor can develop. The difference between angels who generate positive returns and those who subsidize founders' lifestyles is almost entirely explained by the rigor of their evaluation process.

This checklist is not theoretical. It is distilled from the practices of successful angel groups and individual angels who have built portfolios with meaningful, positive returns over decades of investing.

Phase 1: Initial Screening (1-2 Hours)

Before committing to a full due diligence process, conduct a rapid screen to determine whether the opportunity merits deeper investigation. Most deals should be eliminated at this stage.

Market and Opportunity Quick Check

• Is the target market large enough? For a venture-scale return, the total addressable market should be at least $1 billion. Smaller markets can work for lifestyle businesses, but they will not generate the 10x-plus returns that angel portfolios require.
• Is the timing thesis credible? Why is this company being built now? What has changed---technologically, regulatorily, behaviorally---that makes this the right moment? Companies without a clear timing thesis are often solutions looking for problems.
• Is there a defensible competitive advantage? If the idea works, what prevents a well-funded competitor from copying it within eighteen months? Network effects, proprietary data, regulatory moats, and deep technical IP are real advantages. "First mover advantage" is almost never a real advantage.
• Does the business model make intuitive sense? Can you explain how this company makes money in one sentence? If the monetization strategy requires a whiteboard and thirty minutes, the founders may not have figured it out yet.

Founder Quick Assessment

• Do the founders have relevant experience? Not just any experience---relevant experience that gives them insight into the problem and the market.
• Is the founding team complete enough to execute? At minimum, the team needs the ability to build the product and sell it. A solo non-technical founder planning to outsource development is a red flag.
• Have you checked for obvious red flags? A quick LinkedIn review, Google search, and reference check through your network can surface previous failures, litigation, or reputation concerns.

If the opportunity passes initial screening, proceed to full due diligence. Budget 20 to 40 hours for a thorough process.

Phase 2: Team Deep Dive (5-10 Hours)

The team assessment is the most important component of early-stage due diligence. At pre-seed and seed stages, you are investing in people more than products or markets.

Founder Background Verification

• Verify employment and education claims. Founders occasionally embellish resumes. A quick LinkedIn cross-reference and informal back-channel reference checks catch most fabrications.
• Conduct back-channel reference checks. Do not rely solely on references the founder provides. Reach out to former colleagues, bosses, and co-founders through your own network. Ask specifically about integrity, work ethic, and how the founder handles adversity.
• Assess founder-market fit depth. Interview the founders about their domain expertise. How did they identify this problem? What do they know about this market that most people do not? Superficial understanding of the problem space is a major warning sign.
• Evaluate the co-founder relationship. How did the co-founders meet? How long have they worked together? How do they resolve disagreements? Co-founder conflict is among the top reasons startups fail. Look for genuine mutual respect and complementary skills.

Team Composition and Gaps

• Map the current team's capabilities against what is needed. Identify critical skill gaps and assess the founders' plan (and ability) to fill them.
• Review key hires and their terms. If early employees have already been hired, check that equity grants are reasonable and vesting schedules are standard.
• Assess the advisory board critically. Advisors should be actively engaged, not just lending their names. Ask advisors directly about their involvement. If they cannot describe what they do for the company, the advisory board is decorative.
• Evaluate the team's ability to recruit. Can this founding team attract the talent they need? Do they have networks in the relevant technical and industry communities?

Phase 3: Product and Technology Assessment (5-8 Hours)

Even if you are not a technical investor, you can and should evaluate the product and technology with meaningful rigor.

Product Evaluation

• Use the product yourself. If it exists, spend real time with it. Complete the core user journey. Note friction points, bugs, and moments of delight. If the product does not exist yet, review prototypes, wireframes, or demo videos.
• Assess the product roadmap. Is the development plan realistic given the team size and funding? Are the founders prioritizing the right features? A roadmap that tries to do everything simultaneously usually accomplishes nothing.
• Review user feedback. If the product has users, read their feedback---app store reviews, support tickets, NPS survey results, user interviews. What do users love? What do they complain about? Does user feedback align with what the founders told you?

Technical Assessment

• Evaluate the technical architecture. If you lack technical expertise, bring in a technical advisor. The core questions: is the architecture scalable? Is there significant technical debt? Are there architectural decisions that will be expensive to reverse?
• Assess intellectual property. Are there patents filed or granted? Is the core technology proprietary, or built on open-source components that competitors can also use? Review any IP assignment agreements to confirm the company (not individual founders) owns the technology.
• Review the development process. How does the team ship code? What is their testing process? How do they handle production incidents? A disciplined development process is a leading indicator of execution quality.

Phase 4: Market and Competitive Analysis (3-5 Hours)

Founders will always present the market in the most favorable light possible. Your job is to develop an independent view.

Market Sizing

• Build your own market size estimate. Do not accept the founder's TAM/SAM/SOM slide at face value. Use bottom-up analysis: how many potential customers exist, what will they pay, and what market share is realistically achievable?
• Identify market trends and headwinds. Is the market growing, flat, or declining? What macro trends affect demand? Are there regulatory changes on the horizon that could help or hurt?
• Assess market timing. Is the market ready for this solution? Markets that are "too early" have destroyed more angel capital than markets that are too competitive.

Competitive Landscape

• Map all competitors. Include direct competitors, adjacent solutions, and the "do nothing" alternative. Founders who claim they have no competitors are either uninformed or dishonest---neither is a good sign.
• Analyze competitive advantages honestly. For each competitor, assess what they do better and worse than the startup you are evaluating. Where are the genuine points of differentiation?
• Evaluate switching costs. How difficult is it for customers to switch from their current solution to this one? High switching costs can be either an advantage (once customers adopt) or a barrier (to initial adoption).

Phase 5: Financial Analysis (3-5 Hours)

Pre-seed and seed companies have limited financial history, but the financial projections and current burn rate tell you a lot about founder judgment and business viability.

Financial Model Review

• Stress-test revenue assumptions. Work backward from the revenue projections. How many customers are implied? What conversion rates are assumed? What average revenue per customer is modeled? Are these assumptions reasonable compared to industry benchmarks?
• Evaluate the cost structure. Are the expense assumptions realistic? First-time founders consistently underestimate costs, particularly for sales and marketing, customer acquisition, and regulatory compliance.
• Calculate the implied unit economics. Even at early stages, the path to positive unit economics should be visible. If the business model requires customer acquisition costs to decline by 80 percent to become profitable, that is a problem.
• Assess the burn rate and runway. How many months of runway does the company have at current burn? Is the burn rate appropriate for the stage? Companies burning too fast are either undisciplined or over-hiring ahead of product-market fit.

Cap Table and Terms

• Review the cap table for red flags. Excessive equity to advisors, investors with unusual rights, founders who have already sold secondary shares, or dead equity allocated to departed co-founders are all warning signs.
• Understand the terms of all prior investments. What rights do existing investors have? Are there liquidation preferences, anti-dilution provisions, or participation rights that could affect your returns?
• Evaluate the current round's terms. Is the valuation reasonable for the stage and traction? Are the investor protections adequate? At minimum, you should have information rights, pro rata rights for future rounds, and a most favored nation clause.

Phase 6: Customer and Market Validation (3-5 Hours)

This is the phase most angels skip. Do not skip it.

• Talk to current customers or users. Request introductions and conduct independent interviews. Ask about the problem severity, satisfaction with the solution, willingness to pay, and likelihood to recommend.
• Talk to potential customers who have not yet adopted. Why have they not signed up? What would change their mind? What alternatives are they using?
• Talk to customers who churned (if applicable). Why did they leave? Their answers often reveal fundamental product or market issues that current customers will not surface.
• Verify key metrics independently. If the founder claims certain usage statistics, retention rates, or revenue figures, request access to dashboards or raw data. Trust but verify.

Phase 7: Legal Review (2-3 Hours)

• Review corporate formation documents. Confirm the company is properly incorporated, shares are properly issued, and IP is properly assigned.
• Check for outstanding litigation or legal issues. Ask directly and verify through public records.
• Review all material contracts. Customer agreements, vendor contracts, employment agreements, and advisor agreements can contain terms that affect the company's value or operational flexibility.
• Confirm regulatory compliance. If the company operates in a regulated industry, verify that required licenses, registrations, or approvals are in place or have a credible path to approval.

What This Means for Investors

This checklist looks intimidating. That is intentional. Thorough due diligence takes real time and effort, and most angels do not invest enough of either.

Here is the practical reality: you do not need to complete every item on this list for every deal. The depth of your diligence should scale with the size of your check. A $10,000 investment via a SAFE warrants a lighter process than a $100,000 investment in a priced round.

But you need a process. The specific items matter less than the discipline of consistently applying structured evaluation to every investment opportunity. Angels who develop and follow a repeatable due diligence process outperform those who invest on instinct.

The most experienced angels we know can complete a thorough due diligence process in 20 to 30 hours spread over two to three weeks. That investment of time, applied consistently across a portfolio, is the difference between angel investing as a wealth-building strategy and angel investing as an expensive hobby.

Do the work. Every time. No exceptions.