Overview

When syncing employee records across systems using Merge, choosing a stable and universally-resolvable identifier is essential. HRIS platforms vary widely in how they store identifiers, how often those identifiers change, and whether they are truly unique. This guide explains which identifiers to prefer, which to avoid, and how to design a reconciliation strategy that remains reliable as organizations grow and employees change roles.

Recommended unique identifiers (in priority order)

1. Remote ID (strongest & most reliable identifier)

remote_id is the native identifier directly from the source HRIS (e.g., BambooHR, Workday, Justworks). Merge stores this as the authoritative primary key for each employee record. Use as your primary match key whenever possible.

Why it’s the best choice:

• Guaranteed unique within the connected HRIS.

• Immutable.

• Always present, even when other identifiers are not.

• Represents the HRIS record itself, not a human-readable label.

Examples:

• In Justworks → work_id

• In BambooHR → internal employee record ID

• In Namely → employee system ID

2. Employee number / employee ID (reliable when but not always populated)

employee_number is a business-facing identifier that companies assign to employees (e.g., “12345”, “EMP0314”). It often appears on pay stubs, internal systems, or badges. Use employee_number as a secondary identifier or as a complement to remote_id, but do not rely on it universally.

Pros:

• Often treated as a canonical employee number within an organization.

• Human-readable and recognized across internal tools.

• In many HRIS platforms, it is stable and unique.

Cons:

• Not always unique (depends on the organization’s discipline).

• Can change in some systems (e.g., employee type changes, rehiring events).

• Not always populated, especially in SMB-focused HRIS systems.

3. Work email + full name / date of birth (not ideal, but an acceptable fallback)

Work email, paired with an additional field (e.g., full name or date of birth) for improved uniqueness, can function as a fallback when neither remote_id nor employee_number is available.

Strengths:

• Often unique within a single HRIS tenant.

• Commonly available across systems.

Weaknesses:

• Emails change (rebrands, name changes, etc.).

• Not all employees have work emails (hourly, seasonal, contractors).

• Not guaranteed unique across entities.

• Can be recycled.

Identifiers to avoid

SSN / government IDs

Even though they feel universal, they should not be used as a unique identifier.

• High-risk PII → compliance and storage concerns

• Often masked or not returned by APIs

• Inconsistent handling of international IDs

• Prone to data entry errors