Contingent workers now represent a significant and growing share of the US workforce. From independent contractors and freelancers to on-call workers and staffing agency temps, organizations across every sector rely on non-permanent labor to fill skill gaps, manage seasonal volume, and access specialized expertise without the long-term commitment of permanent headcount. But this flexibility comes with legal complexity. This hiring contingent workers guide covers the classification frameworks HR teams must apply, the compliance requirements that govern this workforce, and the risks of getting it wrong.

What Are Contingent Workers?

Contingent workers are non-permanent workers engaged to perform work for a defined period, project, or output. The category is broad and includes several distinct worker types that carry different legal treatment:

  • Independent contractors: Self-employed individuals who provide services under a contract, control their own work methods, and typically work for multiple clients. The defining characteristic is independent control over how the work is performed.
  • Freelancers: Often used interchangeably with independent contractor, though the term is more common in creative, technical, and knowledge-work fields. Freelancers typically set their own rates, own their tools, and manage their own schedules.
  • Temp workers: Hired through a staffing agency, with the agency as the employer of record. The client business directs the work but the agency handles payroll, benefits, and employer taxes.
  • On-call workers: Workers available to report on short notice, compensated only for hours actually worked. Common in healthcare, delivery, retail, and event staffing.
  • Seasonal workers: Employees or contractors hired for a specific season or recurring high-volume period. Classification as employee or contractor still applies based on the nature of the engagement, not the seasonal timing.
  • Statement of work (SOW) contractors: Hired to deliver a defined output or project milestone, rather than time-based work. Often engaged directly without a staffing agency intermediary.

The legal treatment of each category differs substantially. Workers classified as employees—even temporary ones—are subject to FICA, unemployment insurance, workers’ compensation, FLSA overtime, anti-discrimination protections, and state-specific employment laws. Independent contractors are not. This distinction is the foundation of all contingent workforce compliance.

Classification of Contingent Workers: The Legal Tests

No single classification test governs every situation. Different federal and state agencies apply different standards, and HR teams operating in multiple states must understand which test applies in each jurisdiction:

  • IRS Common Law Test (behavioral, financial, and type-of-relationship factors): The IRS evaluates three categories of control. Behavioral control (does the company control how work is done, not just the result?), financial control (does the company control business aspects of the worker’s job—equipment, other clients, profit/loss opportunity?), and the type of relationship (written contracts, permanent vs. project-based, benefits, integral nature of the work). A worker who is controlled behaviorally and financially, and whose work is integral to the business, is very likely an employee.
  • DOL Economic Realities Test (under the FLSA): The DOL evaluates whether the worker is economically dependent on the employer or in business for themselves. Factors include the permanence of the relationship, the worker’s investment in equipment and facilities, the degree of skill required, and the extent to which the work is integral to the hiring entity’s operations. The DOL’s 2024 final rule reinstated a multifactor totality-of-circumstances approach.
  • ABC Test (California AB-5 and similar statutes): Under the ABC test used in California and several other states, a worker is presumed to be an employee unless the hiring entity can prove all three of: (A) the worker is free from the control and direction of the hiring entity; (B) the worker performs work outside the usual course of the hiring entity’s business; and (C) the worker is customarily engaged in an independently established trade, occupation, or business. Prong B is particularly strict—it typically means a technology company cannot use a software developer as an independent contractor.
  • New York’s Freelance Isn’t Free Act: Requires written contracts for freelance engagements worth $800 or more (individually or in aggregate over 120 days), and provides freelancers with payment enforcement rights and protection from retaliation.

When Classification Is Unclear: Use IRS Form SS-8

If your organization is uncertain whether a worker should be classified as an employee or independent contractor, you can submit IRS Form SS-8 requesting a formal determination. This is a proactive way to reduce legal risk before a misclassification dispute arises—though note that the IRS determination is not binding on state agencies applying different tests.

Once classification is determined, compliance requirements follow from the classification. For independent contractors:

  • Obtain a completed Form W-9 before payment for tax identification purposes.
  • Issue a Form 1099-NEC for any contractor paid $600 or more in a calendar year.
  • Do not withhold income tax, Social Security, or Medicare from contractor payments—these are the contractor’s responsibility as self-employment tax.
  • Review the written services agreement to ensure it accurately reflects the independent nature of the engagement, including no employer-provided equipment or exclusive services clauses that could suggest employee status.

For temporary workers hired through a staffing agency:

  • The staffing agency is the employer of record—confirm the agency handles payroll taxes, workers’ comp, and unemployment insurance.
  • Review the staffing agreement for co-employment provisions. In many states, if you exercise sufficient control over the temp’s work, you may be considered a joint employer with liability for wage and hour violations.
  • Do not allow agency temps to access benefits reserved for direct employees unless required by law or your policy explicitly extends coverage.

State-specific rules that affect contingent workforce compliance include California’s AB-5 (strict ABC test), Colorado’s HELP Act, and various state pay equity laws that may require comparable pay analyses for contingent workers performing similar work to direct employees.

Federal and State Laws Are Evolving

The DOL finalized new independent contractor classification rules in 2024 that make it harder to classify workers as contractors under the FLSA. State-level laws—particularly California’s AB-5 and similar bills in New Jersey and Illinois—push further in the employee direction. Review your contingent worker population annually against current law, not just the rules in place when the engagement was first structured.

Risks of Misclassification

Worker misclassification is one of the most financially significant compliance risks in HR. When a worker classified as an independent contractor is later determined to be an employee, the liability can include:

  • Back FICA taxes: The employer’s share of Social Security and Medicare taxes (7.65%) on all wages paid during the misclassification period, plus applicable interest and penalties.
  • Unemployment insurance: Back contributions to federal and state unemployment funds for the reclassification period.
  • Workers’ compensation: Liability for work-related injuries that occurred during the period the worker was misclassified and uninsured.
  • Overtime pay: Under the FLSA, non-exempt employees are entitled to time-and-a-half for hours over 40 per week. If the misclassified worker worked overtime during the engagement, unpaid overtime becomes a liability.
  • Benefits retroactivity: Some benefit plans require retroactive enrollment for newly reclassified employees. Review plan terms carefully.
  • Civil litigation: Workers may file individual or class action lawsuits for wage theft, denial of benefits, or NLRA violations (misclassified workers are excluded from the right to organize). High-profile misclassification cases have resulted in settlements in the hundreds of millions.

Best Practices for Hiring Contingent Workers

HR teams that build systematic practices around contingent worker management significantly reduce their classification and compliance risk:

  • Require classification review before engagement: Establish a pre-hire checklist that applies the relevant classification test—IRS, ABC, or DOL economic realities—before any offer or contract is made to a contingent worker.
  • Use compliant, written services agreements: Every independent contractor engagement should be supported by a written agreement defining scope of work, payment terms, IP ownership, confidentiality, and the independent nature of the relationship. Avoid provisions that look like employment (exclusivity, required hours, company-provided equipment).
  • Maintain a contingent worker register: Document every contingent worker by type (contractor, agency temp, freelancer), engagement dates, scope, and the classification rationale. This register is essential for audits and allows you to identify workers approaching engagement patterns that suggest employee status.
  • Audit your contingent population annually: Review the full contingent roster against current classification law. Workers who have been with your organization for extended periods on rolling contracts warrant particular scrutiny—long-term engagements are a hallmark of employee status under most tests.
  • Train hiring managers on classification rules: Many misclassifications originate with business unit decisions, not HR. Hiring managers who understand what makes a worker an employee—and what creates risk—are a critical line of defense.

Automate Compliance with Treegarden

Treegarden helps HR teams manage contingent worker onboarding, track documentation, and maintain compliance with federal and state laws—all from a centralized platform. Centralizing contractor records, engagement dates, and classification notes means your compliance posture is visible and auditable at any time.

Tools and Resources for Managing Contingent Workers

Managing a contingent workforce without centralized tooling creates significant blind spots. Spreadsheets fail to flag expiring contracts, approaching engagement milestones that suggest reclassification is needed, or workers who are simultaneously engaged across multiple business units in ways that aggregate to an employment relationship. An ATS and HR management platform like Treegarden provides the record-keeping infrastructure, workflow triggers, and reporting visibility that makes contingent workforce compliance systematic rather than reactive—reducing legal exposure and administrative burden for HR teams managing complex, multi-type workforces.

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Frequently Asked Questions

What is a contingent worker?

A contingent worker is a non-permanent worker hired for a specific project or period. They are often classified as independent contractors, freelancers, or temporary workers.

How can I avoid misclassifying workers?

Use the IRS 20-factor test and consult with your HR or legal team. Consider submitting IRS Form SS-8 if there is uncertainty about a worker’s classification.

What are the consequences of misclassification?

Misclassification can lead to back taxes, penalties, legal liability, and potential lawsuits. Employers may also be required to pay unpaid benefits and overtime.

Do state laws affect how I classify workers?

Yes, states like California and New York have strict laws that favor employee classification. Always check state laws before hiring contingent workers.

Can I use an ATS to manage contingent workers?

Yes, an ATS like Treegarden can help manage contracts, track compliance, and streamline onboarding for contingent workers, reducing administrative work.