[REQUIRES APPROVAL] Saves your business identity and document defaults (one row per business; scope is 'default'). timezone is the business clock: an invoice turns overdue at midnight in that zone after its due day, and days_overdue counts days there; unset means Asia/Singapore. Left out, timezone and the text fields keep their saved value, but defaulted fields (default_currency, default_tax_rate_bps, payment_terms_days, invoice_prefix, quote_prefix, template_style) reset, so resend them from sales_settings_read. An agent call waits for the owner's approval. Refuses an unlisted timezone or currency, or a tax rate outside 0-10000, with VALIDATION_ERROR before it waits for approval: send a listed value.