A payroll outsourcing case study rarely says which third-party arrangement it describes. That is the omission worth chasing, because the arrangement decides who the IRS holds responsible when a deposit is late, and under an ordinary payroll service provider arrangement the answer is still the employer.
Everything else in the result belongs in payroll's own units. Payslips and pay runs, not seats.
The First Thing a Payroll Outsourcing Case Study Has to Name
Name the arrangement before you read the number. The IRS treats payroll third parties as four separate kinds and says the outcome is not the same across them, because an employer who uses a third party to perform Federal employment tax functions on its behalf "may remain solely liable for Federal employment taxes, may become jointly and severally liable for such taxes or may be relieved of liability for such taxes" (IRS, outsourcing payroll and third-party payers).
Four rows sit on the agency's own comparison chart, and the last column is the one that decides how much of the exposure actually moves.
| Arrangement | Form filed with the IRS | Who carries the employment tax liability |
|---|---|---|
| Payroll service provider | None required | The employer, not the provider |
| Reporting agent | Form 8655 | The employer, not the agent |
| Section 3504 agent | Form 2678 | The employer and the agent, both |
| Certified professional employer organization | Form 8973 | Generally the organization alone, for the pay it makes to work site employees |
| Source: IRS, third party arrangement chart. |
A published result that never says which row it sits in has left out the fact that decides whether anything transferred.
A Payroll Service Provider or Reporting Agent Assumes None of the Liability
Start with the two arrangements that move the least. A payroll service provider, abbreviated PSP by the IRS, prepares the paychecks, prepares the employment tax returns the employer signs, and makes the federal tax deposits, all under the employer's own employer identification number, or EIN.
A reporting agent differs in the authorization it files rather than in where the liability sits. An employer uses Form 8655 to authorize a reporting agent to perform any or all of the acts a payroll service provider can perform, and a reporting agent may additionally sign and electronically file certain returns (IRS, third party payer arrangements, payroll service providers and reporting agents). What that authorization actually grants, clause by clause, is worked through in how to outsource bookkeeping.
The agency is blunt about what both arrangements do to liability. "An employer's use of either a PSP or a reporting agent does not relieve the employer of its employment tax obligations or liability for employment taxes. These types of third party payers do not assume any of the employer's employment tax liability" (IRS, third party payer arrangements, payroll service providers and reporting agents).
Failure is where that bites. "In the event of default by a third party, the employer remains responsible for the deposit of the federal tax liabilities and timely filing of returns" (IRS, outsourcing payroll and third-party payers). A case study built on either arrangement can honestly report a cost or a turnaround time. It cannot report that the employment tax liability moved, because none of it did.
The Two Arrangements That Move Some of It
An Agent Appointed on Form 2678 Adds a Party Rather Than Replacing One
An appointed agent is the first arrangement where the liability column changes, and it changes by addition. The IRS reads the statute in plain terms: "All provisions of law (including penalties) applicable to an employer apply to an agent so designated. The employer for whom such agent acts remains subject to the provisions of law (including penalties)", which the same page labels joint and several liability (IRS, third party payer arrangements, section 3504 agents).
The comparison chart says it in one line. The employer and the agent "are both liable for paying the client's employment taxes, filing returns, and making deposits and payments for the taxes reported" (IRS, third party arrangement chart).
The filing mechanics move with the liability. The agent files one return for each period on behalf of all the employers it represents, using its own EIN, with Schedule R attached to Form 941, and that EIN also appears on the Forms W-2 filed with the Social Security Administration. Form 940 generally cannot be filed that way, with a narrow exception for agents representing employers who receive home care services paid in whole or in part through a federal, state or local program (IRS, third party payer arrangements, section 3504 agents).
A Certified Organization Can Take It Off You, but Only for Some of the Pay
A certified professional employer organization, or CPEO, contracts to take over "some or all of the employer's federal employment tax responsibilities and obligations", and Form 8973 is what tells the IRS when a contract with a customer starts and ends (IRS, CPEO customers, what you need to know).
The relief is real and it is bounded by who was paid. "Generally, the CPEO is solely liable for paying the customer's employment taxes, filing returns, and making deposits and payments for the taxes reported with regard to remuneration it pays to work site employees (as defined in IRC 7705(e))", while "a CPEO and its customer may both be liable with regard to remuneration the CPEO pays to non-worksite employees" (IRS, CPEO customers, what you need to know).
A work site employee is defined by the site as well as by the contract. The individual has to perform services for the customer under a qualifying contract with the organization, and at a work site where at least 85 percent of the individuals performing services for that customer are covered by such contracts (26 U.S. Code 7705(e)). One person's status therefore turns on the composition of the site they sit at, and a customer can drop below that line and lose the relief for a whole site without anything about the individual changing.
So the relief is decided work site by work site and then dollar by dollar rather than per contract, and a case study quoting one relieved arrangement has said nothing about the pay that sat outside it. How the certification itself is defined, and whether any of this is even the right purchase when the person doing the work sits outside the United States, is worked through in employer of record accounting.
Verifying the Deposits Depends on Whose EIN They Were Made Under
The Electronic Federal Tax Payment System (EFTPS) is "a free system offered by the U.S. Department of Treasury to pay your federal taxes" (IRS, EFTPS). Enrolling in it under your own name and checking the deposits yourself is the standard habit, set out in how to outsource bookkeeping. What almost no payroll case study mentions is that the check stops working as you move down the liability column.
Under a payroll service provider or a reporting agent, deposits are made "on behalf of each client, using the client's separate EIN, according to each client's deposit requirements" (IRS, third party arrangement chart). That is why the IRS tells employers to make sure their provider uses the system, so the employers can confirm that payments are being made on their behalf (IRS, outsourcing payroll duties).
An appointed agent deposits differently. It pays "for tax liabilities the agent has aggregated and reported using the agent's EIN, according to the agent's deposit requirements", so your own EIN is no longer where the whole picture lives (IRS, third party arrangement chart).
A certified organization closes the window. It deposits under its own EIN, and the IRS states the consequence without hedging: "CPEO customers cannot view federal tax deposits and payments made by the CPEO using the Electronic Federal Tax Payment System (EFTPS)" (IRS, CPEO customers, what you need to know).
Read those three together and the pattern is uncomfortable. The arrangement you can audit most easily is the one that leaves the liability with you, and the one that lifts the liability is the one you cannot watch. The appointed agent sits in the worst cell of that grid, because you stay liable and the deposits leave your own EIN. Ask which cell a published result is describing, then ask how its buyer confirmed, during the period being reported, that the deposits were actually made.
The Deposit Due Date Is Set Long Before the Pay Run
A late deposit is a calendar event, and the calendar is fixed in advance. There are two deposit schedules, monthly and semiweekly, and which one applies is settled before the year begins from the taxes reported in a lookback period, with more than $50,000 reported for that period making a Form 941 filer a semiweekly schedule depositor (IRS, Publication 15).
The deadlines follow from the schedule rather than from the payroll cycle. A monthly schedule depositor deposits the taxes on payments made during a month by the 15th day of the following month. A semiweekly schedule depositor deposits for Wednesday, Thursday and Friday paydays by the following Wednesday, and for Saturday, Sunday, Monday and Tuesday paydays by the following Friday (IRS, Publication 15).
One rule overrides both. Accumulate $100,000 or more in taxes on any day during a deposit period and the tax has to be deposited by the next business day, on either schedule, and a monthly schedule depositor that crosses the line becomes a semiweekly schedule depositor the next day and stays one for at least the rest of that calendar year and the following calendar year (IRS, Publication 15).
That is why an off-cycle run matters more than its size suggests. A bonus payroll concentrates liability into a single day, and the deadline can move with it while the provider's service levels stay exactly as agreed.
The penalty for missing that date falls on the person required to make the deposit, unless that person shows the failure "is due to reasonable cause and not due to willful neglect" (26 U.S. Code 6656). What the tiers cost is tabulated in what outsourced bookkeeping leaves out.
Report the Result in Payslips and Pay Runs
Payroll has its own units, and a result stated in seats has changed the subject. A headline percentage with no base under it fails for the same reason, worked through in reading a CPA firm outsourcing cost savings case study. Five figures carry payroll specifically, and the first of them is payroll's version of the per-unit cost set out for invoices in an accounts payable outsourcing case study.
Cost per payslip and cost per pay run. Total payroll cost for a period divided by the payslips produced in it, then the same total divided by the number of runs. Report the run count beside both. Neither per-unit figure has to move when the calendar fragments, because more runs raise the total and the payslip count together, so a weekly cycle and a monthly one at the same headcount can post the same cost per payslip and the same cost per run while the annual total differs several times over. What moves is the total, so read the per-unit figures against runs per period and headcount, and include the funding approvals, the reconciliation and the review that stayed inside, not only the provider's invoice.
Payroll error rate per thousand payslips. Payslips that carried an error, divided by payslips issued in the same period, scaled per thousand. Count the error at the payslip, because the payslip is where an employee feels it. One mis-set deduction code lands on every payslip in a run while a late timesheet lands on exactly one, so keep a separate count of distinct causes if you also want to know how many things went wrong. Agree what counts as an error before the measurement starts, or the definition drifts toward whoever is reporting it.
Off-cycle and retroactive run rate. An off-cycle run is a payment made outside the scheduled calendar, and a retroactive run recalculates pay already issued. A retroactive run is rework by definition, while an off-cycle run may be planned, like a bonus payroll, or it may be a correction, so split the count by cause before anyone reads the rate. Both create a deposit obligation of their own on the day the money moves. Report them as a share of total runs.
Corrections issued on Form W-2c. Form W-2c corrects errors on a Form W-2 already filed with the Social Security Administration and supplies the corrected statement to the employee (IRS, About Form W-2c). Count them per season and split them by cause, because a correction created by data the employer supplied late says nothing about the provider.
Time from timesheet close to funding. The elapsed time from the timesheet cutoff to the moment the money for net pay and for the tax deposit is available in the account it will be drawn from. Both ends need naming in the agreement, because a slow interval either moves payday or leaves nobody time to catch an error before the money goes.
The Payroll Control Boundary
Four questions draw the line, and each one has a payroll answer rather than a general one.
Who Funds the Account
The IRS treats the movement of payroll money as a fact worth examining. Its issue indicators for a third-party payer arrangement include "Payroll funds being transferred from the employer to a third party" and "Wages not paid from the employer's bank account(s)" (IRS, third party payer arrangements, payroll service providers and reporting agents).
Settle in writing which of those describes yours. A provider instructing a debit against an account you own sits in a different position from one that holds your money for a day, and the two can be sold under the same word.
Who Releases the Direct Deposit File
Preparing a run and releasing it are separate acts, and the second is the irreversible one, because a direct deposit file that has reached the bank is a set of payments rather than a draft. Keep the release with a named person inside your firm, and keep whoever prepared the run out of that step.
Who May Change an Employee Bank Record
A bank record change is the highest-value edit in a payroll system, and it usually arrives as a message from an employee rather than as a form. Verify it against the record you already hold, or by a route you initiated, and keep whoever makes the change apart from whoever releases the run. The equivalent control on the supplier side, and the fraud it exists to stop, is covered in an accounts payable outsourcing case study.
Who Holds the Federal Payment Credentials
Enrollment in the federal payment system belongs to the employer, in the employer's own name, whatever the arrangement says about who presses the button. Your own enrollment is worth most under a payroll service provider or a reporting agent, where the deposits are made under your EIN and your own payment history is the check.
Under an appointed agent or a certified organization the deposits sit under someone else's number and your enrollment will not show them, so that verification has to be written into the agreement rather than assumed. Keep the enrollment anyway, because it is the one account in the chain you control directly. Give it away and the only evidence you hold about a provider comes from the provider.
The Payroll Case Study Worth Running
None of the published ones settle this for your firm. One quarter of one payroll does.
Capture the five figures across a full quarter before anything moves: cost per payslip and per pay run, errors per thousand payslips, off-cycle and retroactive runs as a share of the total, corrections issued and their causes, and the time from timesheet close to funding. Then move only the record work, leave funding, release, employee bank records and the payment credentials exactly where they were, and measure the same calendar quarter again once the ramp is behind you. Name the arrangement in writing on both sides of that comparison, because a result that changed the arrangement and the provider at once has measured two things.
Firms that run payroll for clients stand on the other side of the sentence. If a client appoints your firm on Form 2678, the liability column above is describing your firm, jointly with the client. If your firm is a reporting agent on Form 8655 it is not, and the same table says so (IRS, third party arrangement chart). Either way, every boundary question here is one you are holding for each client at the same time.
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