You will quickly learn that Tag 528 (OrderCapacity) and Tag 47 (ExecInst) are enforcement points that can cancel or reject your orders when you misstate your role or execution intent.
Tag 528 (OrderCapacity) tells counterparties and exchanges whether you act as Agency, Principal, Riskless Principal or another capacity. If you declare Agency but route trades as a dealer, or you mark Principal without inventory/treatment that matches clearing and reporting rules, downstream systems will flag and kill the order for compliance violations. Exchanges and brokers enforce these semantics during pre-trade checks, gateway validation and post-trade reporting.
Tag 47 (ExecInst)FillOrKill, DoNotReduce, ShortExempt or other instructions. If you attach a short-sale related ExecInst (a ShortLocate or ShortExempt indicator) without meeting the locate/borrow requirements, risk controls and market rules can immediately cancel the order. Similarly, conflicting instructions between OrderCapacity and ExecInst (e.g., agency-only routing plus principal-only execution flags) trigger automated kills.
For operational safety you must: validate account type and regulatory permissions before setting OrderCapacity; confirm borrow/locate status and any exemption before tagging ExecInst for short activity; align order routing metadata (on-behalf-of, clearing firm, contra party) with declared capacity; and log all decisions for audit. Pre-trade checks usually include borrow-locate APIs, inventory checks, and rule engines that compare your Tag 528 and Tag 47 values against market permissions.
When an order dies, check audit trails for mismatched fields: the typical culprits are incorrect OrderCapacity, missing locate confirmation tied to short-sale ExecInst, or mutually incompatible execution flags. To avoid kills, make deterministic mapping rules in your order gateway: map account metadata to a single canonical OrderCapacity, only set short-related ExecInst when a verified locate exists, and surface compliance rejections immediately so you can correct and re-submit.