The number that frames the risk: approximately 77% of Rocket Lab's backlog sat with its top five customers as of December 31, 2025, according to the company's FY2025 Form 10-K. A year earlier, the FY2024 Form 10-K put the same figure at approximately 69%. Concentration rose even as the backlog itself grew — the growth and the risk moved together.
Concentration cuts both ways. On the upside, a heavily concentrated backlog signals that large, sophisticated buyers — including government and anchor commercial customers — have committed real money. On the downside, the company itself flags the obvious hazard: its filing warns that backlog customers could experience changes that affect their commitments, and a single large customer's delay or cancellation would move the forward-revenue line disproportionately.
The revenue side carries the same shape. Rocket Lab's FY2024 disclosure noted that its largest customers together accounted for approximately 51% of revenue. When roughly half of recognized revenue and three-quarters of backlog rest on a small set of names, the quality of the order book is inseparable from the health of those specific programs.
For a markets desk, this is the disciplined read: Rocket Lab's order book is large and growing, but its durability is a function of a handful of programs staying funded and on schedule. The concentration figure is not a red flag on its own — it is a sensitivity to watch each time a customer's own funding cycle turns. Primary disclosure on sec.gov; surfaced via EdgarBeast.