Few automation failures are as costly and visible as duplicate orders. When your automated workflow creates the same order twice in QuickBooks, ships the same package twice via ShipStation, or bills a customer double, the consequences ripple through accounting, fulfillment, and customer trust. Duplicate orders are not random glitches; they stem from specific, preventable design flaws in how automations handle triggers, retries, and state management.
Why Duplicates Happen: The Root Causes
Understanding the mechanics of duplication is the first step toward prevention. There are five primary causes that account for nearly every duplicate order we encounter in production automation systems.
1. Trigger Re-firing: Polling-based triggers in platforms like Zapier check for new records on a schedule. If the source system's API does not provide a reliable "last processed" marker, the same order can be picked up by consecutive polling cycles. Webhook-based triggers can also fire twice if the source system implements retry logic when it does not receive an acknowledgment quickly enough.
2. Retry Without Idempotency: When an API call fails mid-execution and your automation retries the entire flow, any steps that already completed successfully will execute again. If you created the order in QuickBooks but the subsequent ShipStation step failed, retrying the entire scenario creates a second QuickBooks entry.
3. Concurrent Executions: If two instances of the same scenario run simultaneously and both pick up the same order, you get two outputs. This happens when scenario scheduling intervals are shorter than execution time, or when webhooks fire in rapid succession.
4. Status Misreads: If your trigger watches for orders with status "new" and your automation changes the status to "processing" at the end of the flow, any orders that arrive between the trigger check and the status update can be processed again on the next cycle.
5. Manual Replay Without Checks: After fixing a failed automation, operators sometimes replay incomplete executions without checking whether the downstream system already received partial data during the original attempt.
Figure 1: Without idempotency checks, retrying a partially-failed automation creates duplicates in the system that succeeded on the first attempt.
Prevention Strategy 1: Idempotency Keys
The most robust prevention mechanism is idempotency: the principle that processing the same input multiple times produces the same result as processing it once. Assign every order a unique identifier, typically the source system's order ID, and check for that identifier before creating any record. In Make.com, use a Search module to query the destination system before the Create module. If the order already exists, skip creation and proceed to the next step.
Prevention Strategy 2: Status Flagging
Update the source record's status immediately after the trigger fires, not at the end of the workflow. Mark the order as "processing" in the very first step, before any data transformation. This prevents the next trigger cycle from picking up the same order. If the workflow fails, a separate error handler should reset the status to allow re-processing, but only after a delay to avoid race conditions.
Prevention Strategy 3: Deduplication Tables
Maintain a dedicated deduplication table, either in a database, Google Sheet, or Make.com Data Store, that logs every order ID your automation processes. At the start of each execution, check the order ID against this table. If it exists, skip processing. If it does not, add it to the table before proceeding. This external check is independent of any single system and catches duplicates regardless of their source.
Detecting Existing Duplicates
If you already have duplicates in your system, detection is the first step toward cleanup. Run a query against your QuickBooks or accounting system grouping by the external order reference number. Any reference number appearing more than once indicates a duplicate. For ShipStation, compare shipment counts against order counts for the same date range. Automated reconciliation reports run weekly can catch duplicates within days rather than weeks.
Figure 2: A deduplication table provides a reliable external check that prevents duplicates regardless of trigger behavior.
Fixing Duplicates After They Occur
When duplicates are found, the cleanup approach depends on the system. In QuickBooks, void or delete the duplicate transaction and verify the remaining one has the correct amounts. In ShipStation, cancel the duplicate shipment before it prints a label. For inventory systems, recalculate stock levels after removing duplicates, as each duplicate artificially decremented inventory. Document every correction for your accounting records.
Duplicate orders are a systemic problem that requires systemic solutions. Band-aid fixes like "just check manually" fail at scale. If your order-to-cash workflow is producing duplicates, the architecture needs revision. For more on data integrity in automation, see our guide on inventory sync discrepancies.
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