Series A is the round that proves the product works. Series B is the round that proves the business works. The metrics bar is sharper, the diligence deeper, and the questions investors ask change from "can this be a company?" to "can this be a $1B+ company?"
What investors look for
Series B investors are pattern-matching against historical winners. The four questions they're answering:
- Is the growth durable? Are you still growing 80%+ YoY at increasing scale? Or is growth slowing because the market isn't as big as you said?
- Are unit economics improving? CAC payback dropping, NRR climbing, gross margin expanding — these compound into a much bigger business at scale.
- Can the team execute at 5x scale? 50 → 250 people in 18 months. The leadership team has to scale too — not just the founders.
- Is the moat real? Are competitors catching up, or are you pulling ahead? Series B is when network effects, data advantages, or distribution leverage need to start showing.
The metrics that matter
B2B SaaS
- $5-10M+ ARR, growing 80-120% YoY at this scale.
- NRR > 110%, ideally 120%+ (best companies are 130%+).
- Logo retention > 92% annual.
- CAC payback < 18 months (under 12 for SMB; 18-24 for enterprise).
- Gross margin 70%+, ideally trending up.
- Burn multiple (net burn / net new ARR) under 1.5.
Consumer / marketplace
- Meaningful scale: 10M+ MAUs or $100M+ annualized GMV.
- Long-term retention: D365 retention significantly above category benchmarks.
- Profitable unit economics — at least one cohort or geo where unit profitability is clear.
- Network effects visible: organic growth share, supply density, retention by cohort.
Below these numbers? You're in Series A territory or doing a Series A2 / extension, not a Series B. Forcing a B at Series A metrics rarely works and usually means worse terms.
The deck changes
Series B decks lead with metrics, not story. Typical structure:
- Cover
- One-line company description + three headline metrics
- Company snapshot: customers, ARR, team, geography
- Growth trajectory: ARR by month, last 24 months
- Cohort retention curves (NRR, logo retention)
- Unit economics: CAC, LTV, payback, gross margin trends
- Customer detail: top customers, ACV distribution, expansion
- Sales motion: how you sell, by segment, with conversion math
- Product roadmap (1-2 slides)
- Market: TAM evolution, current penetration, expansion paths
- Team: org chart, key hires, hiring plan
- Financials summary
- The ask: amount, valuation range, use of funds
The story slides from Series A (problem, solution, why now) shrink to a single slide at Series B. Investors at this stage already believe in the category — they're underwriting your execution.
Targeting the right firms
Series B is dominated by specific firms. Different mix than Series A:
- Growth-stage specialists: Insight Partners, Iconiq, Bessemer Growth, Lead Edge, Coatue, Tiger.
- Multi-stage firms with strong B/C practices: a16z, Sequoia, Accel — but typically only at the very top of any class.
- Sector-specialist growth funds: Battery (vertical SaaS), Forerunner (consumer), G2 (marketplaces).
Filter your target list to firms with at least 5 Series B leads in your category in the last 24 months. Random Series B targeting wastes 10-15 weeks.
The process
Series B processes are longer and heavier than Series A:
- Weeks 1-3: Prep. Deck, model, data room, customer reference list, recent customer wins as case studies.
- Weeks 4-8: First meetings. Cluster aggressively — investor calendars at this stage are tight.
- Weeks 9-14: Partner meetings, deep diligence, customer reference calls.
- Weeks 15-20: Term sheets and negotiation. Multiple term sheets is the norm at Series B.
- Weeks 21-28: Legal close. Series B legal is heavier than Series A; expect 4-6 weeks of legal alone.
What changes about the founder job
Series B founders fundraise less than they expect, but they fundraise differently:
- Less story, more spreadsheet. Investors want monthly cohort tables and unit economics by segment.
- Reference depth. Series B investors call 8-12 references — customers, former colleagues, your past managers, competitors. Pre-brief carefully.
- Earlier process kickoff. Start B prep when you have 12+ months of runway. The process eats 4-6 months of founder attention.
- Board involvement. Existing board members will often be involved in lead selection. Manage their expectations early.
Common Series B failure modes
- Forcing the round at A metrics. If your numbers aren't B-quality, raise an extension and grow into B metrics.
- Picking the highest valuation lead. Series B leads take board seats and become your primary partner for 4-7 years. Partner fit dwarfs valuation differences.
- Underestimating diligence. Series B diligence surfaces every cap-table hairball and unsigned founder agreement. Audit and clean up well before kickoff.
- Stretching financial projections. Series B investors discount projections aggressively. Conservative beats aggressive every time.
Run the cap table math first with our cap table simulator — Series B + ESOP refresh can dilute founders by 25%+ in a single round. Plan for it.