TikTok Shop and the website both counted every sale — real ROAS was 1.8x

The situation

A UK fashion brand had both a TikTok Shop and a standalone Shopify website. They were running TikTok ads that drove traffic to both. TikTok Ads Manager was showing a 3.6x ROAS. Shopify showed half the revenue TikTok was claiming. The brand was scaling based on the 3.6x figure.

The problem

TikTok Shop automatically sends purchase events via its native integration when a sale occurs on TikTok Shop. The brand had also implemented TikTok pixel + Events API on their Shopify website, which sent purchase events for Shopify sales. When an ad drove a TikTok Shop purchase, TikTok Shop reported it AND the CAPI (which was also connected) reported it — same purchase, two events, no shared event_id between the two systems.

What we did

1. Identified dual purchase reporting: TikTok Shop events + CAPI events firing for same sales
2. Disabled redundant CAPI integration for TikTok Shop purchases — TikTok Shop native events are the authoritative source for Shop sales
3. Kept CAPI integration active only for Shopify website purchases with website-specific event_id
4. Verified in TikTok Events Manager: purchase count now matching combined TikTok Shop + Shopify orders in Shopify admin
5. Re-evaluated campaign ROAS with accurate data — 1.8x vs previous 3.6x

Why it worked

TikTok Shop's native event integration is automatic and can't be disabled from the advertiser side — it's part of the TikTok Shop merchant agreement. Brands that implement additional CAPI events alongside TikTok Shop will double-count every in-app purchase unless they explicitly scope their CAPI to website-only purchases using conditional event filtering.