What it is
Churn is lost recurring revenue from customers ending (or sometimes reducing) contracts. Finance must distinguish logo churn from revenue churn, and full churn from contraction.
How it’s calculated
Dollar churn sums ARR lost from cancellations in the period. Logo churn counts customers lost. Gross vs net churn depends on whether expansion offsets are allowed in the same metric — prefer separate waterfall lines.
Where it breaks
Churn breaks when non-renewals sit in limbo past period end, when contraction is labeled churn, or when free/trial logos inflate logo churn rates.
In the board pack
Show churn as an explicit waterfall component and as an input to GRR/NRR — not a single ambiguous percentage.
Keep the written definition stable across close, the board pack, and diligence so the same word never means two math models.