Display Serial Number on Form

I assume you are attempting to display the Serial Number of an active task on this task form?  I believe a valid Serial Number will usually only exist while the Task/Client event is active:

When integrating with SmartForms, it will create a State and add a rule to open this task on the form; in this context, the applicable Serial Number will be available:

In the open worklist item rule:

In this Rule, the Serial Number can be mapped to a data label control in the out put mapping for the application Activity:

Hi SanaShah,

  Start Workflow Action rule is only responsible to start workflow, once process instance is created  rule execution will completed and return process instance id in output mappings.

• SN is combination of “Process Instance ID”(for e.g. 9865) and “Activity Instance Destination ID”( for e.g. 21)
• Which is appears as    Process Instance ID_ Activity Instance Destination ID (9865_21).
• As we already have Process Instance ID, we are only required to get “Activity Instance Destination ID” to generate SN.

To get “Activity Instance Destination ID” follow below steps

• Add rule “Execute a SmartObject method “and select SmartObject as “Activity Instance Destination” which is available under Workflow reports.

• Now concatenate both Data Label’s having “_” in between, which return SN.

Let me know if this helps you.