You need to add a custom field to the HR Profile that syncs with an external payroll system. Which table should be extended or modified?
The HR Profile record is stored in sn_hr_core_profile, so custom fields that must sync with external payroll belong on that table. Extending it preserves the profile's link to the employee record and keeps the integration mapping consistent.
Why this answer
The HR Profile table (sn_hr_core_profile) is the central location for user-specific HR data.