The verdict in three sentences
For a 220-person engineering firm in New York, an expense management SaaS (USD 7 to 13 per user per month) costs USD 74,000 to 137,000 over 4 years, versus USD 40,000 to 83,000 for a custom app (USD 22,000 to 50,000) including maintenance. Custom development clearly wins once your client rebilling rules are specific: project codes, caps per contract, expenses rebilled at cost or at a flat rate. If your rules are standard, SaaS remains the fastest option to deploy.
The real cost of expense reports in an engineering firm
With 9,000 expense reports a year, the cost goes beyond admin work. Engineers traveling to client sites (New Jersey, Connecticut, upstate New York, Canada) incur expenses that largely must be rebilled. When allocation to the right project fails, those expenses are never invoiced.
| 2026 indicator (order of magnitude) | Spreadsheet and paper | Tooled process |
|---|---|---|
| Entry time per report (employee) | 12 to 20 min | 2 to 4 min with OCR |
| Review time per report (accounting) | 6 to 10 min | 1 to 2 min |
| Reimbursement delay | 20 to 45 days | 5 to 10 days |
| Billable expenses not rebilled | 3 to 6% | under 1% |
| Sales tax and category errors | 5 to 10% of reports | under 1% |
| Lost receipts | 2 to 4% | near zero (instant photo) |
Across 9,000 reports, saving 12 minutes of entry and 6 minutes of review frees about 2,700 hours a year, more than one full-time equivalent.
SaaS or custom: the 4-year total cost
| Item | Market SaaS | Custom app |
|---|---|---|
| License per user per month | USD 7 to 13 | USD 0 |
| Annual subscription (220 users) | USD 18,480 to 34,320 | USD 0 |
| Initial development | USD 0 to 3,500 of configuration | USD 22,000 to 50,000 |
| Annual maintenance and hosting | Included | USD 4,500 to 8,300 |
| Receipt OCR | Included or USD 1 to 2 per user add-on | USD 0.01 to 0.03 per receipt via API |
| Project rebilling connector | Often unavailable or USD 5,500 to 16,500 | Included in scope |
| 4-year total cost | USD 74,000 to 137,000 | USD 40,000 to 83,000 |
The calculation assumes stable headcount. If you grow from 220 to 300 employees, SaaS rises by a third, while custom stays flat. Conversely, below 80 users, SaaS is almost always cheaper.
The business rules that justify custom
An engineering firm rebills expenses according to each client contract. SaaS tools handle categories and caps well, but rarely the full contractual logic.
| Business rule | Standard SaaS | Custom |
|---|---|---|
| Allocation to an ERP project code | Yes, via imported list | Yes, synced in real time |
| Different caps per client | Rarely | Yes |
| Rebilling at cost or flat rate per contract | No | Yes |
| Handling fee markup (5 to 10%) | No | Yes |
| Generation of client invoice lines | Manual CSV export | Automatic in the ERP |
| IRS 2026 standard mileage rate | Yes | Yes |
| CAD expenses for Canada missions | Yes | Yes, with daily rate |
Mini case study
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Sarah, CFO of a 220-person engineering firm in New York, manages 9,000 expense reports a year, including USD 1,050,000 of expenses billable to clients. Her unbilled rate reaches 4%, or USD 42,000 lost every year. She chooses a custom app at USD 37,500 with USD 6,000 of annual maintenance, connected to her project ERP. The loss rate drops to 0.8%, recovering USD 33,600 a year, plus 2,700 hours of entry and review freed up. Over 4 years, the app costs USD 61,500, versus about USD 105,000 for a SaaS at USD 10 per user, which would not have handled her rebilling rules.
FAQ
How much does a custom expense management app cost in 2026?
Budget USD 22,000 to 50,000 depending on connectors (ERP, payroll, bank) and the complexity of rebilling rules. Maintenance and hosting cost USD 4,500 to 8,300 per year.
Is receipt OCR reliable?
2026 OCR engines extract amount, date, tax and merchant with 92 to 97% accuracy on US receipts. The employee confirms in one click, bringing entry down to 2 to 4 minutes per report.
Are digital receipts accepted by the IRS?
Yes, electronic images of receipts are accepted if the system ensures integrity, legibility and retrieval. The app should timestamp and keep files for at least 3 to 7 years depending on your retention policy.
How long does deployment take?
A first release ships in 8 to 12 weeks. A one-month pilot on a 30-person department precedes rollout to the whole company.
At how many users does custom become profitable?
As a rule above 120 to 150 users over 4 years, or from 80 users if you have specific rebilling rules. Below that, a well-configured SaaS is enough.
Let's scope your project. Describe your volumes, ERP and rebilling rules: we will price your app between USD 22,000 and 50,000 with go-live in 8 to 12 weeks. Detailed quote within 48 h. WhatsApp +221 77 596 93 33.
Mohamed Bah
Fondateur, Kolonell
Passionate about digital and entrepreneurship in Africa, Mohamed has been helping Sénégalese businesses with their digital transformation since 2020. Founder of Kolonell, he believes every SME deserves a professional and accessible online présence.
