An HRIS business case is usually written to get approval and never looked at again. A case worth writing is one you would be content to be measured against a year later, which changes which benefits you claim.
Count the administrative time you can actually remove
Measure the current cycles before you buy: hours to onboard a starter, to process a leave request, to answer a payroll query, to assemble the monthly report. Multiply by volume, and be honest that some of the saved time is spread thinly across many people rather than released as a role. That is still a benefit; it is just not a headcount saving.
Error and penalty avoidance is real but needs evidence
Late filings, incorrect pay, missed certification renewals and documents that could not be produced all have costs, and an HRIS reduces them. Use your own incident history rather than an industry figure. A case built on a vendor's benchmark for the cost of a payroll error will not survive the first serious question.
Count every cost, including the internal ones
Licence, implementation, data migration, integration, training, and the internal time of the person who will administer it. Then add renewal uplift and headcount growth over the period. Business cases that fail at review usually fail here rather than on the benefits, because the costs presented were the quote rather than the project.
Write down how you will measure it afterwards
Pick three measures, record the baseline before go-live, and put a review in the calendar for a year later. Cycle time for onboarding, payroll error rate and time to produce the monthly report are good choices because they are measurable and attributable. A case with a scheduled review is also, in practice, a better implementation.
Questions people ask about hris roi
What payback period is realistic?
Commonly two to three years once implementation is included. Cases claiming under a year usually omit internal cost.
Is reduced headcount a credible benefit?
Only if a role genuinely goes. Otherwise claim capacity released and say what it will be used for.
What is most often missed?
Data migration effort and the ongoing internal administration of the system.