Raising a Series A feels like validation. But roughly 60-70% of startups that raise a Series A never make it to Series B. The reasons are surprisingly predictable - and many of them are visible during due diligence if you know where to look.
Premature scaling
The most common killer. A startup raises $5-10M and immediately hires 30 people, opens a second office, and launches in three new markets. Six months later, they realize the product-market fit they thought they had was actually limited to one segment in one geography.
What due diligence catches: Look at the retention data before the raise. If month-over-month retention is below 80%, the product-market fit isn't strong enough to scale. No amount of hiring fixes a retention problem.
The founder-market fit was wrong
Some founders are great at getting from 0 to 1 but struggle with 1 to 10. The skills needed to build an MVP and get first customers are different from the skills needed to build a sales team, manage a growing organization, and navigate enterprise deals.
What due diligence catches: Look at the founder's track record with growing teams. Have they managed more than 5 people before? Have they built processes that work without them being in every meeting?
Unit economics that never worked
At pre-seed and seed, investors often accept negative unit economics with the assumption they'll improve with scale. Sometimes they do. Often they don't.
If a startup's customer acquisition cost is $500 and the average customer pays $50/month with 6-month retention, the LTV is $300. That math never works no matter how much you scale.
What due diligence catches: Run the unit economics yourself with the startup's real numbers. Don't accept the founder's projections of future CAC reduction - look at the trend over the last 6 months.
Technical debt catches up
The code that was "good enough" to launch an MVP becomes a liability when you need to ship features fast, onboard enterprise customers, or handle 10x the traffic. We've seen startups spend their entire Series A runway rebuilding infrastructure instead of growing.
What due diligence catches: A technical review before investing reveals whether the codebase can support the growth plan. Test coverage, architecture quality, and security posture all matter.
The market shifted
This one's harder to predict, but it's worth noting. Markets change fast. A competitor launches with better funding. A platform changes its API. Regulation shifts. The startup that looked well-positioned six months ago suddenly isn't.
What due diligence catches: A thorough competitive analysis reveals how defensible the startup's position really is. If the moat is "we're first" with no technical or network effects, the risk is high.
The lesson for early-stage investors
You can't prevent all failures. But you can avoid the predictable ones. Most post-Series A failures have roots that were visible at the seed stage - weak retention, unsustainable economics, fragile code, or founders who haven't demonstrated the skills needed for the next phase.
Thorough due diligence doesn't guarantee success. But it dramatically reduces the chance of investing in a startup with visible structural problems.
