Start with the cash-flow question
A software project can have a high first-year return and still require money before the first saving arrives. Conversely, a small setup payment may be recovered quickly even when recurring subscriptions leave only a modest annual benefit. ROI and payback describe different parts of that cash-flow pattern. Neither automatically measures risk, validates the value of staff time or includes discounting.
Define three amounts before dividing
For this illustration, the setup cost is paid once at the start. The monthly benefit is the value of usable hours recovered plus any separately counted avoided costs. The subscription is paid each month. Benefits begin immediately and stay constant; this is an explicit simplifying assumption, not a rollout forecast.
Setup payback = upfront setup / positive monthly net benefit
First-year ROI = (annual gross benefit − first-year cost) / first-year cost × 100
First-year cost includes twelve subscriptions plus the one-time setup payment. The payback denominator instead uses the benefit remaining after the subscription has been paid. Dividing all first-year costs by gross monthly benefit mixes two timing conventions and does not describe recovery of the upfront payment.
A complete worked example
Assume 10 hours of usable work are saved each month, valued at $30 per hour. The subscription is $100 per month and setup is $600. There are no other savings.
| Quantity | Calculation | Result |
|---|---|---|
| Monthly gross benefit | 10 × $30 | $300 |
| Monthly net benefit | $300 − $100 | $200 |
| Setup payback | $600 / $200 | 3 months |
| First-year cost | $600 + 12 × $100 | $1,800 |
| First-year benefit | 12 × $300 | $3,600 |
| First-year ROI | ($3,600 − $1,800) / $1,800 | 100% |
Immediately after setup, the cumulative position is −$600. It becomes −$400 after month one, −$200 after month two and $0 after month three under these assumptions. That cash-flow check explains the three-month recovery without relying only on a percentage.
When “no payback” is the useful answer
If the monthly benefit falls to $80 while the subscription stays $100, the project loses $20 per month before recovering any setup cost. Increasing the comparison period does not create payback under those unchanged assumptions. A calculator should explain the lack of positive net monthly benefit rather than report a finite recovery time from gross benefits.
If setup is zero and monthly net benefit is positive, the modeled upfront recovery time is zero. ROI can still be undefined when the total entered cost is zero. An undefined percentage is different from a zero-dollar cash benefit or a zero-percent return.
Test what can actually be realized
Recovered staff time is not automatically cash saved. It can be useful capacity, but only value it as new collected revenue or avoided cost when that assumption is supportable. Avoid counting an error reduction both as recovered staff hours and as a second avoided expense. Include implementation work that is absent from the quoted setup cost in a separate budget.
Save a baseline in the accounting software, payroll software or time-tracking calculator. Lower only the hours saved, then compare the two results. This shows the effect of weaker benefit realization while leaving the price and setup assumptions unchanged.
Limits and background
The recovery model assumes level monthly net benefits. It excludes a deployment delay, taxes, discounting, replacement costs and changing subscription prices. A fractional month is a proportional estimate, not a promised calendar date. DOE’s cost-analysis methodology also explains why simple payback alone does not capture the whole life-cycle value of a project; the software example and arithmetic here are independently specified.