Expansion Revenue
Expansion revenue is additional recurring revenue from your existing customers, on top of what they originally paid. It comes from upsells (moving to a higher plan), cross-sells (buying an add-on), and seat or usage growth (more people or more volume). It's the cheapest revenue you'll ever earn, because the customer is already onboarded, already trusts you, and costs nothing new to acquire.
For a lean founder, expansion is where the durable money lives. Acquiring a new customer is expensive and slow; growing an existing one is fast and high-margin. A product that gets more valuable as a customer uses it, more data, more seats, more workflows, has expansion built into its DNA. Track it as a distinct line from new business so you can see whether your base is growing or just being replaced. Strong expansion is the engine behind net revenue retention above 100%.