In partial cancellation, the cancellation date is any date between the asset start date and the asset end date. Based on the end date populated, the Billing decides the type of cancellation. If you want to cancel the asset during the legacy period (cancellation date same as the asset start date or the first billing date), partial cancellation is not allowed, and Billing displays an error message. If you want to cancel the asset after the migration date into Conga Billing, partial cancellation is allowed.