Comma-separated related objects to return in full instead of as IDs. Accepted values: claims, claims.account, claims.attachments, claims.branch, claims.contact, claims.cost_center, claims.project, claims.tax_rate, employee, employee.reimbursements_account, journal, reimbursements_account, reimbursements_account.parent. Nested relations are joined with a dot. Pass journal to replace the journal ID with its object (ID, date, currency, reference, notes and timestamps). Documents without a journal still return null. Journal line items are retrieved separately with GET /v1/journal-line-items/?journal={journal_id}.