How do I define the policy for deferring social security deductions during probation periods?

By default, social security deductions aren't deferred, but you can establish a deferral policy for a specific tax reporting unit (TRU) on the TRU-level calculation card.

Select the Manage Legal Reporting Unit Calculation Cards task in the Setup and Maintenance area, and then open the calculation card for the tax reporting unit. Add a Common Information calculation component to the card (if it doesn't already exist), and then select the deferment type applicable for this TRU in the Component Details section.