LinkedIn's Conversions API is the most useful integration for B2B teams running paid social, and the most temperamental about input data. The platform matches incoming events to user profiles primarily on hashed email. If the email you send does not match the one on the user's LinkedIn profile, the event is dropped from optimisation.

The business vs personal split

Most users sign up to LinkedIn with their work email. They then sign up to your demo form with their personal email, because they do not want to receive sales emails on their work account. The result: your CRM has Jane's personal email; LinkedIn has Jane's work email; the match rate looks dismal.

Send everything you have

LinkedIn's API accepts multiple matching keys per event. Send all of them:

• Hashed email (whichever one you have).
• The company domain extracted from the email if it looks corporate.
• First name and last name, hashed.
• Job title from the form, if present.
• The LinkedIn click ID (li_fat_id) from the landing URL.

The click ID is the strongest signal because it is direct: LinkedIn sees the user click the ad and lands them on your site with the click ID appended. If you capture and forward it, the match is essentially guaranteed.

Capture the click ID early

Add a small snippet to your site that reads li_fat_id from the URL on first hit and stores it in a first-party cookie:

const params = new URLSearchParams(location.search);
const liFatId = params.get('li_fat_id');
if (liFatId) {
  document.cookie = `_li_fat_id=${liFatId}; max-age=2592000; path=/; secure; samesite=lax`;
}

On every conversion event, your tagging server reads the cookie and forwards the value as acxiomId in the LinkedIn payload. The LinkedIn template in sGTM has this mapping built in if you select "use first-party cookie."

What to skip

Do not send IP address. LinkedIn does not use it for matching and including it raises GDPR concerns without any benefit. Do not send the company domain when the email is from gmail or outlook; the noise hurts more than it helps. And do not send phone numbers; LinkedIn matches on them poorly compared to other platforms.