Transaction ID

A transaction ID is the value that makes a conversion unique — usually the order number, transaction number, or lead ID from your own system. You send it on the conversion pixel or postback, and it does two jobs: it appears in your reports as the Transaction ID column so you can reconcile a conversion against your books, and it deduplicates — re-firing the pixel with the same transaction ID updates the existing conversion instead of minting a new one. It is the single most important field for keeping your conversion counts honest.

Why every conversion needs one

Pixels fire more than once in the real world: a customer refreshes the confirmation page, a server retries after a timeout, an amount gets revised. Each of those re-fires would create a separate conversion — and a separate payout — unless the platform can recognize them as the same event. The transaction ID is that recognition key. With it, retries and refreshes are safe; without it, there's no way to catch them and every fire counts.

A worked example

Your checkout fires:

https://track.yourbrand.com/conv?ll_cid=abc123&txn=order-8837&rev=250
        

The customer's connection hiccups and the page reloads, firing the identical request again. Because txn=order-8837 matches an existing conversion, the platform updates that one conversion rather than recording a second $250 sale. Later you correct the order amount to $275 and re-fire with the same txn — the conversion updates in place to $275. One order, one conversion row, always.

Contrast that with leaving the placeholder unreplaced: if the pixel ships txn=TRANSACTION_ID literally, the platform treats it as no key, and each fire records as its own conversion. A forgotten substitution costs you idempotency — so always replace it with a real per-conversion value.

Transaction ID vs conversion ID

They are different numbers. The transaction ID is yours — your order number, sent on the pixel. The conversion ID is the platform's — a unique number it assigns to the conversion, quotable to support. You store the conversion ID to tie your record to theirs; you send the transaction ID so they can dedup.

How this works in LimeliJourney

In LimeliJourney the transaction ID is the txn parameter, central to tracking and deduplication. The generated pixel ships with txn=TRANSACTION_ID as a placeholder you must replace with a real value — your order or transaction ID is ideal. Re-firing the same txn returns the same original conversion ID, and a server fire with &format=json hands that conversion ID back so you can store it in your CRM. Transaction-ID dedup is on by default; leaving the placeholder in only costs idempotency, never your data, and the Pixel Log notes when it happens.