HR Org Structure as You Scale: Which HR Duties Matter (and When)
Most companies don't build an HR function. They wake up one day and realize they're missing one.
It usually goes like this. The founder does payroll. Then the office manager does payroll, benefits, onboarding, and "that one weird employee thing." Then you hit 60 people, somebody files a complaint, a state agency sends a letter, and everyone looks at each other like, wait, who owns this?
I've been an HR executive and I've worked inside a PEO, so I've seen this from both sides of the table. The pattern barely changes: HR gets built in reaction to pain, not ahead of it. That's backwards, and it's expensive.
So here's the cheat sheet I wish more founders had. What HR duties actually matter at each stage, who your first HR hire should be, and what you can hand off to someone else.
HR duties by company size: the stage-by-stage breakdown
Headcount isn't the only thing that matters (multi-state, remote teams, or M&A work get complicated faster), but it's the best rough guide. A lot of federal rules switch on at specific employee counts, so let's use those.
Stage 1: 1–25 employees: "Don't get anything wrong"
At this size, HR is mostly admin. Boring, but non-negotiable.
Payroll and tax filings. Done right, on time, every time.
I-9s for every hire. From employee number one. No exceptions, no "we'll catch up later."
State registrations. Withholding and unemployment accounts in every state where someone works. Hire one remote person in a new state and you've got a new set of obligations.
Worker classification. Employee vs. contractor, exempt vs. non-exempt. This is where small companies get bitten the most.
Basic benefits admin. If you offer benefits, someone has to actually run open enrollment.
A starter handbook. Short, legal, current.
Heads up: Title VII and the ADA kick in at 15 employees, and federal COBRA applies at 20 (most states have their own "mini-COBRA" rules for smaller employers). Your policies need to be ready for that before you get there, not after.
Stage 2: 25–50 employees: "Stop winging it"
This is where the office-manager-does-HR model starts to crack.
Recruiting process. Consistent job descriptions, interview steps, and offer letters.
Onboarding. A real checklist, so new hires don't spend week one hunting for a laptop.
HRIS. Get off the spreadsheets. Pick a system that can grow with you.
Manager basics. Your first-time managers are now your biggest legal risk. Train them.
Getting ready for 50. Because 50 is a big one.
Stage 3: 50–100 employees: "The compliance cliff"
Fifty is where federal law starts paying attention to you.
FMLA. Applies once you have 50+ employees for 20 or more workweeks in the current or prior year. Employees are eligible if they work at a site with 50+ employees within 75 miles (plus the tenure and hours requirements). You need a leave process, notices, and tracking.
ACA employer mandate. At 50+ full-time employees including full-time equivalents, you're an Applicable Large Employer. That means offering affordable, minimum-value coverage and filing 1094-C/1095-C forms. Part-timers count toward FTEs. People miss this all the time.
Leave management. FMLA, ADA accommodations, state paid leave, workers' comp, all tangled together. Someone needs to own it.
Performance management. Simple, consistent, documented. If you have to defend a termination, "we talked about it" won't cut it.
Employee relations. Complaints and investigations need a neutral, trained person, not the CEO's best friend.
Stage 4: 100–250 employees: "Structure or chaos"
EEO-1 reporting. Private employers with 100+ employees file annually (federal contractors can hit this earlier). The federal WARN Act also applies at 100 employees, which matters if you're ever planning a layoff.
Compensation structure. Pay bands, leveling, and a philosophy you can explain. Pay transparency laws in a growing number of states make this a must.
Learning and development. Especially for managers. You can't keep promoting your best individual contributors and hoping.
HR team, not HR person. One generalist can't do recruiting, ER, benefits, and leave for 150 people. They'll burn out, or things will quietly slip.
Stage 5: 250+ employees: "People strategy"
HR business partners aligned with business units.
Specialists in total rewards, talent acquisition, and HR operations/analytics.
Workforce planning, succession, and engagement data that actually feeds leadership decisions.
A senior People leader at the leadership table.
Quick reference: HR duties by stage
1–25 employees: Payroll, I-9s, state registrations, classification, basic benefits, handbook. Key thresholds: Title VII/ADA at 15; COBRA at 20.
25–50 employees: Recruiting process, onboarding, HRIS, manager training. Key thresholds: Prep for 50.
50–100 employees: FMLA, ACA compliance, leave management, performance, employee relations. Key thresholds: FMLA at 50 (within 75 miles); ACA ALE at 50 FTEs.
100–250 employees: EEO-1, comp structure, L&D, building a specialized HR team. Key thresholds: EEO-1 at 100; WARN at 100.
250+ employees: HR business partners, specialists, workforce planning, People strategy. Key thresholds: Varies by state and contracts.
Your first HR hire: generalist, coordinator, or leader?
This is the decision I see companies get wrong most often. Usually in one of two ways.
HR coordinator. Great at execution: paperwork, onboarding, HRIS data. But a coordinator can't tell you whether your leave policy is compliant or how to handle a harassment complaint. Don't hire a coordinator and expect strategy.
HR generalist. The right first hire for most companies between 30 and 75 employees. Broad, hands-on, and can handle most day-to-day issues. Pair them with outside expertise for the tricky stuff.
HR leader (manager/director/head of People). Makes sense once you're closing in on 100, growing fast, or cleaning up a mess. Hiring a VP of People at 30 employees usually means a very expensive person doing data entry.
Who should HR report to?
Ideally, the CEO or COO. Not because HR needs a fancy title, but because HR needs to be able to say "no" to managers, and sometimes to executives.
Reporting to Finance is common, and it can work. But be honest about the tradeoff: HR will get measured on cost, and the people side tends to get squeezed. If HR reports to Finance, make sure the CEO still has a direct line to it.
How do you know if HR is reporting to the wrong person? See the FAQ below.
What to keep in-house vs. what to outsource
You don't have to build everything yourself. You do have to own it. Outsourcing the work isn't the same as outsourcing the responsibility.
Your main options (more on PEO, ASO, or something else in my breakdown of the differences):
PEO. Bundles payroll, benefits, workers' comp, and compliance support under a co-employment model. Very useful early: you get big-company benefits and admin coverage without an HR team.
ASO. Similar admin services, but no co-employment. You keep your own benefit plans and more control.
Payroll provider + broker. The do-it-yourself route. More control and more work.
Fractional HR. Senior HR expertise part-time, for strategy, compliance, and the hard conversations.
Here's the honest take from someone who's worked inside one: a PEO can be the right call at 15 people. But companies often outgrow it somewhere between 50 and 200 employees. Benefits options get rigid, the fees get harder to justify, and "HR support" turns out to be a ticket queue.
Generally keep in-house as you grow: culture, employee relations, performance management, manager coaching, and comp decisions.
Generally fine to outsource: payroll processing, benefits admin, compliance filings, background checks, and specialized projects like comp benchmarking.
Warning signs your HR structure is lagging
If a few of these sound familiar, your HR structure is behind your headcount:
Nobody can tell you, quickly, how many employees you have in each state.
Managers handle complaints on their own and HR finds out later. Or never.
Leave requests get tracked in someone's inbox.
Two people in the same role are paid very differently, and nobody can explain why.
Your "HR person" is also your office manager, your executive assistant, and your event planner.
You passed 50 employees and nobody checked what changed.
Your PEO renewal went up again and you're not sure what you're getting for it. (If that's you, here's how to leave a PEO without dropping anything.)
FAQ
When should a company hire its first HR person?
Most companies benefit from dedicated HR somewhere between 30 and 50 employees. Before that, a PEO, payroll provider, or fractional HR can cover the basics. Waiting until after 50 usually means you're catching up on compliance.
What HR laws apply at 50 employees?
The big two federal ones are FMLA (50+ employees, with eligibility tied to 50 employees within 75 miles) and the ACA employer mandate (50+ full-time employees including FTEs). Many states have their own rules that kick in earlier.
What is the ideal HR-to-employee ratio?
There's no magic number, but many growing companies land around one HR person per 50 to 100 employees, depending on complexity, how many states you're in, and what you outsource.
Should a 100-person company still use a PEO?
No. At this size, the cost of bringing HR in-house is typically less than the cost with the PEO. Further, the relationship feels clunky and HR is not positioned to support the business strategically.
How do you know if HR is reporting to the wrong person?
Watch for these signs:
HR is stuck in survival mode. This is common when HR reports to a COO who's fighting today's fire and bracing for the next one, so HR ends up reacting instead of planning. When your people processes are still clunky but you have an SOP for everything, you know you’ve hit a wall here.
Costs are under control, but growth is painful. This is common when HR reports to the CFO: the budget looks good, but hiring, onboarding, and manager support can't keep up.
Politics rule. People complain that the organization has become political. When the most political people gain the most influence and your top performers are left frustrated, HR needs more visibility, and it might need a new boss.
If more than one of these sounds familiar, it's time to rethink the reporting line. For most growing companies, that means moving HR closer to the CEO.
If you’re a Founder who is nervous about whether you have the time to dedicate to the function, that should tell you that you’ve got the wrong person leading the function. A solid HR leader will handle the majority of issues without your involvement and keep you apprised of what may “bubble up” without needing you to jump in and solve the problem.
Need a second set of eyes?
If you're growing and your HR setup still looks like it did at 20 people, you're not alone. Most companies I talk to are right there. I help companies with roughly 50 to 200 employees figure out what HR structure they actually need, whether their PEO still makes sense, and how to make the move if it doesn't. Get in touch with My Next Level HR and let's talk about where you are.
This post is for general information only and isn't legal advice. Employment laws vary by state and change often, so check with an employment attorney about your specific situation.