`service_start_date` (service period start)
service_start_date (service period start)
service_start_date records when the purchased service period begins. Bookkeeping uses service period dates to support periodization decisions without reopening the vendor invoice document.
Service periods matter for costs such as rent, insurance, hosting, and subscriptions where the invoice timing does not match when the service is consumed.
Example values: 2026-02-01, 2026-01-01.