> ## Documentation Index
> Fetch the complete documentation index at: https://docs.sourcemedium.com/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# Attribution in SourceMedium

> How SourceMedium uses UTMs and attribution models (last-click and MTA) to attribute orders and revenue

SourceMedium supports multiple attribution approaches. This guide explains what we mean by attribution, where it comes from, and which knobs typically cause differences between tools.

## Two common attribution layers

### Last-click attribution (UTM-based)

Last-click attribution assigns credit to the **most recent** tracked marketing touch before a purchase.

* Primary inputs: UTM parameters, landing pages, referrers
* Common use: channel reporting, performance trends, and reconciliation to analytics tools

Related docs:

* [UTM setup](/help-center/core-concepts/attribution/utm-setup)
* [What is last-click attribution?](/help-center/faq/account-management-faqs/what-is-last-click-attribution)
* [How can I improve my last-click attribution?](/help-center/faq/account-management-faqs/how-can-i-improve-my-last-click-attribution)
* [Attribution Source Hierarchy](/data-transformations/attribution-source-hierarchy) - How we prioritize between data sources

### Multi-touch attribution (MTA)

Multi-touch attribution assigns credit across multiple touch points within a lookback window.

* Primary inputs: first-party event streams (e.g., GA4), marketing data, and modeled purchase journeys
* Common use: understanding incremental contribution across channels, creatives, and landing pages

Related docs:

* [First-party attribution](/help-center/core-concepts/attribution/first-party-attribution)
* [MTA overview](/mta/mta-overview)
* [MTA FAQs](/mta/mta-faqs)

### Zero-party attribution (survey-based)

Zero-party attribution uses **customer-reported** survey answers (for example: “How did you hear about us?”) to understand top-of-funnel discovery that tracking often misses.

Related docs:

* [Zero-party attribution](/help-center/core-concepts/attribution/zero-party-attribution)
* [Survey best practices (HDYHAU)](/help-center/faq/account-management-faqs/best-practices-in-setting-up-a-post-purchase-hdyhau-survey)

## Common reasons attribution differs between tools

* Different lookback windows (e.g., 7-day vs 28-day vs 120-day)
* Missing or inconsistent UTMs (especially for email/SMS and paid social)
* Cross-domain or checkout tracking limitations
* Post-purchase edits or delayed revenue recognition

If you’re reconciling against Shopify, start with: [Why don’t Executive Summary & Shopify match?](/help-center/faq/data-faqs/why-dont-the-executive-summary-and-shopifys-sales-report-match)