> ## Documentation Index
> Fetch the complete documentation index at: https://docs.simplifi.work/llms.txt
> Use this file to discover all available pages before exploring further.
# How to Create a New Payroll Rule in the Engine
The Payroll Rules Engine is Simplifi's logic that your system uses to decide how, when, and how much to pay each person. Simplifi automates this logic by applying the right rule to every timesheet, shift, and contract and allows you to define custom rules and logic for specific events.
Start by filling in the name and validity dates.
**Who**
Who determines which people the rule will apply to. Select which rule is appropriate using the drop-downs. Remember that multiple rules can be created.
**When**
When determines the trigger for this rule to be applied. Multiple triggers can be made.
**Then**
Then determines what action to take based on the previous rules.