When auto-tagging of Microsoft Click ID (MSCLKID) is enabled, Bing Ads will automatically add a unique click ID to the landing page URL. This click ID will be included in all subsequent UET events fired whenever the same customer visits your page, thereby allowing you to track the conversion from this customer on your site.
As of December 11, 2017, Bing Ads automatically enables auto-tagging of Microsoft Click ID when you create a new conversion goal. You may, however, have older conversions goals in which auto-tagging of Microsoft Click ID is not yet enabled. Below, you can learn the benefits of Microsoft Click ID and how to enable it if you haven’t already.
Auto-tagging of Microsoft Click ID makes sure that no conversion tracking falls through the cracks. The UET tag on your website reports user activity, including the Microsoft cookie, to Bing Ads. In some cases, the Microsoft cookie can't be returned due to browser settings (for example, third-party cookie blocking) or browser type. If you don't have auto-tagging of Microsoft Click ID enabled, these conversions aren't tracked.