The best practice is to always book Campaign Manager 360 tags using the 'Campaign Manager 360 tag' creative type. Using this creative type saves you from having to add any additional macros for click tracking, and keeps the discrepancy of clicks between Campaign Manager 360 and Ad Manager under 2%.
It’s possible to traffic a Campaign Manager 360 tag as a custom creative to allow for additional formatting of the creative, such as the addition of a third-party tracking pixel. In these rare cases, you must add the Google Ad Manager click macro to the Campaign Manager 360 tag in order to track clicks properly, as well as the CacheBuster macro for certain tag types.
Here’s an example of a Campaign Manager 360 tag in the “INS” format, which requires only a click macro (cache busting is built into the tag):
<ins class='dcmads' style='display:inline-block;width:728px;height:90px' data-dcm-placement='Nxxxx.site-keyname/Byyyyyyy' data-dcm-rendering-mode='script' data-dcm-param-dcadv='zzzzzzz' data-dcm-click-tracker='%%CLICK_URL_UNESC%%'> <script src='//www.googletagservices.com/dcm/dcmads.js'></script> </ins>
When a Campaign Manager 360 tag is trafficked as a custom creative, Ad Manager treats the Campaign Manager 360 tag as a third-party tag and therefore doesn't report clicks without the Google Ad Manager click macro. Additionally, you should expect to see a larger discrepancy in delivery numbers, as you would with any third-party ad server.
For more help on inserting macros into the correct location, see Macro overview. To learn more about the Campaign Manager 360 INS tags, see Use the INS tag.