How Tyre Registrations Work

Source: `vehicle_tyre_registrations_controller.rb`

• Tyre registration requires the invoice to have a vehicle attached; invoices without a vehicle cannot have tyre registrations
• Registration requires a Base TIN and at least one of DOT week or DOT year; the Full TIN is constructed from base TIN + week + year
• New tyre registrations are automatically flagged for TireMetrix TRP sync
• Outstanding tyre registration lists exclude open, deleted, and voided invoices; only processed invoices with pending registrations are shown

Support scenarios

• "I can't add a tyre registration to this invoice" → The invoice must have a vehicle attached. Add a vehicle to the invoice first, then create the tyre registration.
• "Tyre registration says TIN is invalid" → A Base TIN is required, plus at least one of DOT week or DOT year. Ensure the base TIN is entered and at least one date component is provided.
• "A tyre registration isn't showing in the outstanding list" → Outstanding registrations exclude open, deleted, and voided invoices. Check the invoice status -- it must be processed for the registration to appear in the outstanding list.