sending offline measurment data - does cid have to match the original cid?

Question

I need to send a cart status update based on an offline activity. My customers will add items to their cart online via the website but the final checkout and purchase happen offline.

Here is my question: In the example below, a checkout step is updated. Does the client_id provided in this step have to match the original client_id used when the web user started their cart originally?

Measuring Checkout Options

v=1                                   // Version.
&tid=UA-XXXXX-Y                       // Tracking ID / Property ID.
**&cid=555                              // Anonymous Client ID.**
&t=event                              // Event hit type
&ec=Checkout                          // Event Category. Required.
&ea=Option                            // Event Action. Required.
&pa=checkout_option                   // Product action (checkout_option).
&cos=2                                // Checkout step.
&col=FedEx                            // Checkout step option.

Answer 1

Client ID is how Google Analytics tracks each individual user throughout their multiple sessions. So, yes- if you want that payload to be associated with the same user, then the CID will need to match- otherwise you'll be artificially inflating your user count (as well as severing the contextual data from that user).

You can parse the cookie that GA stores in the browser to obtain the CID and then fill it there. Not sure what language you're writing in, but there are plenty of snippets out there for parsing the GA cookie. You could also store the CID when it is initially generated in your own session data to be used later while offline. For example:

ga(function(tracker) {
  var clientId = tracker.get('clientId');
  console.log(clientId);
});

You could also provide your own CID from the start that you generate yourself and tell Google Analytics to use. This might be overkill for your situation, but I wanted to mention it as an option.