To authenticate Paylocity, you will need to provide the following information:
Client ID
Client Secret
Company ID
This guide will walk you through finding or creating those credentials within Paylocity.
Paylocity Web Services - Access Request Form
How to fill in the form:
The Client Contact Information should contain information about your company (for example, your HR personnel)
The Vendor / Third-Party Contact Information should contain information for the company you are connecting to
Under "Briefly describe use case," mention "we are using Merge to connect."
You can ignore the "Webhook Push Notifications" section
Permissions:
If you do not need Pay Statements, Deductions, & Earnings, fill out the following:

If you do need Pay Statements, Deductions, & Earnings fill out the following:

Note: Get Employee is a required permission to authenticate the linking flow, but only endpoints needed for your integration should be selected. For example, if you don’t need Pay Statements, Deductions, or Earnings, remove those from the permissions.
The email body should contain the following:
Subject: Requesting Client ID and Client Secret
Hi Paylocity team, can we get access to a Client ID and Client Secret for API access? (https://www.paylocity.com/our-products/integrations/api-library/) We have attached the form specifying relevant permissions. Note: There may be a cost associated with the API setup & gathering of credentials from Paylocity.
Paylocity will provide you with your Client ID and Client Secret, which you can enter into the linking flow. For further information, you can find full details on Paylocity's website here.

Your Company ID is the ID you used to login into Paylocity, and it will be the same ID you see in the upper left-hand corner of your Paylocity portal. Enter your Company ID into the linking flow.
If your Company ID includes “CS”, only enter the number that follows it. In all other cases, enter the ID exactly as it appears, because the values are case-sensitive.



If you are using multiple companies within your Paylocity account which you want to link, enter any additional company IDs on the Enter optional company IDs step
Company IDs are case-sensitive, so please enter it exactly as it appears in Paylocity
Separate multiple IDs with a comma, for example 12345,ABCDE,F0001
Do not include a space after the comma
Enter None if you do not want to link multiple companies
Click Next once done

When providing optional companies, be aware that the same person may be employed by more than one company during the course of their employment. In these cases you would see the same employee several times (once for each company).