ROI of a back-office digitalisation project: the calculation
A method to calculate the ROI of a back-office digitalisation project: baseline, 3-year TCO, gains, ROI and payback, with a worked example.
Expert note: This article was written by our chartered accountancy firm. Information is current as of 2026. For a personalised review of your situation, contact us.
Quick answer. The ROI of a back-office digitalisation project is calculated by comparing net annual gains to the total project cost: ROI = (gains minus costs) / costs. The calculation relies on a measured baseline, a 3-year TCO and a payback expressed in months.
You are hesitating to invest in a tool to digitalise your supplier invoices, expense reports or invoicing. The question is not "should we digitalise" but "how much does it return, over what period, and at what real cost". This article does not list software: it gives you the method to calculate the ROI of a back-office digitalisation project, from quantifying gains to payback.
To understand why and how to digitalise, see our articles on accounting digitalisation and accounting automation. Here, we do the maths.
ROI in two formulas, and one trap#
Return on investment rests on two simple formulas:
- ROI = (gains minus costs) / costs, expressed as a percentage.
- Payback = investment / net annual gains, expressed in months or years.
The trap lies elsewhere: the reliability of the result depends entirely on the quality of your two ingredients, the gains and the costs. A ROI built on inflated gains and a cost stripped of change management is not a ROI, it is a sales pitch. The discipline of the calculation matters more than the formula.
Step 1: define the scope#
Do not try to measure the ROI of "digital transformation" as a block. Pick a single, homogeneous process:
- purchasing and supplier invoices (approve-to-pay workflow);
- expense reports;
- customer invoicing and dunning;
- payroll and social declarations.
A narrow scope can be measured. A blurry scope never can, and that is precisely what makes so many ROI figures unverifiable.
Step 2: establish the measured baseline#
The baseline is the current state, quantified. How many hours per month do you really spend on the target process? At what loaded hourly cost? How many errors, reminders, late penalties?
The reflex to ban: the rough guess. Ask the person involved to log their real time over two to four weeks. Without a measured baseline, you will never be able to prove the gain afterwards.
Step 3: estimate gains, conservatively#
Here are the gains to quantify, from the most tangible to the most indirect:
| Gain | How to quantify it |
|---|---|
| Time saved | Hours saved per month, converted to loaded hourly cost then to a fraction of an FTE |
| Removal of re-keying | Hours of double entry eliminated |
| Fewer errors and penalties | Cost of late penalties and credit notes avoided |
| Shorter close | Days of close saved, valued as team availability |
| Better DSO | Faster collections: cash gain, sometimes savings on overdraft interest |
| Better traceability | Harder to quantify: mention it without overstating it |
Golden rule: take the low assumption. If you think you will save "60 to 80% of the time", calculate on 60%. A conservative ROI that materialises is worth more than a flattering ROI that disappoints.
Step 4: cost the 3-year TCO#
Total cost of ownership (TCO) is not limited to the advertised subscription. That is the most common mistake. Here are the components to include over three years.
TCO components#
| Component | Nature | When |
|---|---|---|
| Subscriptions and licences | Recurring | Each year |
| Integration and setup | One-off | Year 1 |
| Data migration | One-off | Year 1 |
| Team training | One-off, sometimes recurring | Year 1 then new joiners |
| Maintenance and support | Recurring | Each year |
| Change management | One-off | Year 1 |
| Hidden costs (internal time, double entry during transition) | One-off | Switchover phase |
The two items owners most often forget: change management (support, the team's time to adopt the tool) and the hidden transition costs (double entry while the old and new systems coexist). They can represent a significant share of Year 1.
Step 5: compute ROI and payback#
Worked example (illustrative figures)#
The amounts below are fictional and serve only to show the mechanics of the calculation. Case: digitalising the supplier invoice cycle of an SME.
| Item | Amount |
|---|---|
| Baseline: current time | 25 h/month, i.e. 300 h/year |
| Loaded hourly cost | 35 € |
| Current annual cost of the process | 10,500 € |
| Time gain retained (low assumption 60%) | 6,300 €/year |
| Late penalties and credit notes avoided | 1,200 €/year |
| Gross annual gains | 7,500 € |
| Year 1 TCO (subscription + integration + migration + training + change) | 9,000 € |
| Recurring TCO (years 2 and 3) | 3,000 €/year |
| Total cost over 3 years | 15,000 € |
| Cumulative gains over 3 years | 22,500 € |
| ROI over 3 years | (22,500 minus 15,000) / 15,000 = 50% |
| Net annual gains (after recurring cost) | 4,500 €/year |
| Payback | 9,000 / 4,500 = approx. 2 years |
Reading: here, the project pays back in about two years and yields a 50% ROI over three years. Change the gain assumption or the hidden cost, and the result tips. That is the whole point of a transparent calculation: it makes the assumptions debatable.
The calculation procedure in 6 steps#
- Define the scope: a single process (purchasing, expense reports, invoicing, payroll).
- Establish the baseline: current time and costs measured, not estimated.
- Estimate the gains conservatively, on a low assumption.
- Cost the 3-year TCO, including change management and hidden costs.
- Compute ROI and payback with the two formulas.
- Track and reassess three to six months after rollout.
Our take#
In the SME files we support in financial steering, the ROI of a digitalisation project is rarely decided by the price of the subscription. It is decided by two things: having measured the baseline before starting, and having honestly budgeted change management. A firm registered with the Ordre des experts-comptables d'Île-de-France can help you build this calculation, but above all help you hold it: set the baseline, cost the TCO, then come back to measure the real gain. It is this final step, almost always skipped, that distinguishes a steered investment from a bet.
The right reflex: start small, prove the ROI on one process, then extend. See also how to digitalise the supplier cycle with an approve-to-pay workflow, often the first project with the best gain-to-cost ratio.
The underestimated risk#
The risk owners see least: announcing a ROI at decision time, then never verifying it. The project launches, the tool runs, but nobody comes back to compare actual gains with the baseline. The result: it is impossible to know whether the investment paid off, or to decide on extending it to other processes. After-the-fact tracking is not a formality, it is what turns spending into a management decision.
Common case#
A services SME contacts us after subscribing the whole team to an expense-report tool, disappointed not to "see the gain". Rebuilding the baseline afterwards, the finding is twofold: administrative time did fall, but training had been neglected, so half the staff kept entering paper claims in parallel. The hidden cost of this double entry had absorbed part of the gain. With the calculation redone, scope tightened and adoption fixed, the ROI becomes readable again. The lesson: a poor ROI often comes from poor deployment, not a poor tool.
Points to watch in 2026#
One driver stands out in any back-office ROI calculation this year: electronic invoicing. Receiving electronic invoices becomes mandatory for all companies on 1 September 2026 (date to be verified against the official calendar applicable to your situation). In practice, digitalising the supplier cycle is no longer only an efficiency project, it is a compliance requirement. This changes the calculation: part of the investment would have been incurred anyway. Include it in the TCO, but also reason in terms of the opportunity cost of a late start.
Checklist before validating the calculation#
- The scope is limited to a single process.
- The baseline is measured, not estimated.
- Gains are retained on a low assumption.
- The TCO includes change management and hidden costs.
- Recurring costs for years 2 and 3 are quantified.
- Payback is expressed in months or years.
- A post-rollout reassessment date is set.
Frequently asked questions
How do you calculate the ROI of a digitalisation project?+
Apply ROI = (gains minus costs) / costs. First establish a measured baseline of the process, estimate annual gains conservatively, cost the total over three years, then divide the net gain by the cost. Express the result as a percentage.
What is the TCO of a digitalisation project?+
The TCO, or total cost of ownership, adds up over three years the subscriptions, integration, setup, data migration, training, maintenance, change management and hidden costs such as double entry during the transition. It is the TCO, not the headline price, that serves as the denominator of the ROI.
Which gains should you quantify?+
Time saved converted into full-time equivalents, removal of re-keying, fewer errors and penalties, a shorter close, a better DSO and therefore cash, and traceability. Quantify the tangible gains first, mention the others without overstating them.
What payback should you target for a digitalisation project?+
There is no universal threshold. Many well-scoped back-office projects target a return over a few months to two or three years. The narrower the scope and the higher the baseline, the faster the return. The right period depends on your ability to tie up the initial cash.
How do you avoid overstating the gains?+
Always take the low assumption, base the calculation on a measured rather than guessed baseline, do not count the same gain twice, and honestly budget change management. Above all, plan a reassessment after rollout to compare the actual gain with the estimate.
Should electronic invoicing be included in the calculation?+
Yes. With receiving electronic invoices becoming mandatory for all companies on 1 September 2026 (to be verified against your situation), part of the investment in the supplier cycle is a matter of compliance. Include it in the TCO and also reason in terms of the opportunity cost of a late start.
Key takeaways#
- The ROI of a digitalisation project is calculated with two simple formulas, but its reliability depends on the quality of the gains and costs retained.
- The measured baseline is the condition without which ROI remains unverifiable.
- The 3-year TCO must include change management and hidden transition costs, not just the subscription.
- Take the low gain assumption: a conservative ROI that materialises beats a flattering ROI that disappoints.
- The 2026 electronic invoicing requirement turns supplier-cycle digitalisation into a compliance project to factor into the calculation.
- Post-rollout tracking, almost always forgotten, is what distinguishes a steered investment from a bet.
To structure this calculation for your case, the firm offers support in finance digital transformation, built on tools such as Pennylane.
Article published by Hayot Expertise, registered with the Ordre des experts-comptables d'Île-de-France. Informative scope: a ROI calculation and an investment decision must be tailored to your situation, your real data and the regulations in force.
Article written by Samuel HAYOT
Chartered Accountant, registered with the Institute of Chartered Accountants.
Regulated French accounting and audit firm based in Paris 8, built to support companies across France with a digital and decision-oriented approach.
Sources
Official and operational sources cited for this page.
This topic is part of our service Finance transformation | Automation & dashboards
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