The verdict in three sentences
For an office drawing up 60 evidence reports (constats) a month, re-entering data at the office costs 60 to 120 working hours monthly, the equivalent of half to a full position. A custom mobile evidence app (EUR 20,000 to 50,000 excl. VAT depending on scope) captures photos, voice notes, geolocation and qualified timestamps directly on site, then pushes a draft report into the office's practice software. Payback usually lands between 8 and 18 months, provided file integrity and the export to your practice software are locked in the specification from day one.
What the app must guarantee for a report to hold up
A French commissaire de justice report carries evidential weight through the officer, but disputes usually target the attachments: photo date, location, possible editing. The app must therefore produce an evidence chain a judge can read, not just nice pictures.
| Technical component | Evidential role | 2026 order of magnitude |
|---|---|---|
| Qualified timestamp (eIDAS, qualified provider) | Enforceable certain date for each file | EUR 0.05 to 0.30 per token depending on volume |
| SHA-256 hash of every photo and video | Proves no modification after capture | Included in development |
| GPS geolocation + accuracy in metres | Places the shot on the premises | Included, EUR 0 licence |
| Locked capture (no import from gallery) | Prevents insertion of external photos | 2 to 4 development days |
| Signed audit log (who, when, which device) | Internal traceability and dispute support | 3 to 6 development days |
| Local encryption + offline sync | Reports in basements, no-signal areas | 5 to 10 development days |
| Annexed PDF export + archive of originals | Attachments to the deed, retention | 4 to 8 development days |
At 60 reports a month and an average of 40 photos per report, you use about 2,400 timestamp tokens a month, i.e. EUR 120 to 720 monthly depending on provider and service level. Timestamping only the file batch per report (one global hash) brings this down to EUR 3 to 18 a month, an option to validate with your professional chamber and insurer.
What the project costs, from minimum viable to full version
| Scope | Main features | Budget excl. VAT (2026 order of magnitude) | Timeline |
|---|---|---|---|
| Field MVP | Timestamped photos, notes, geolocation, PDF export | EUR 20,000 to 28,000 | 8 to 10 weeks |
| Office standard | MVP + transcribed voice dictation, report templates, offline | EUR 28,000 to 38,000 | 10 to 14 weeks |
| Integrated | Standard + export to practice software, signature, dashboard | EUR 38,000 to 50,000 | 14 to 20 weeks |
| Hosting and backup (France) | Server, encrypted storage, daily backup | EUR 80 to 250 per month | Ongoing |
| Evolutive maintenance | iOS/Android updates, fixes, small changes | 15 to 20% of initial budget per year | Ongoing |
| Off-the-shelf solution (evidence SaaS) | Standard template, little integration | EUR 40 to 120 per user per month | 2 to 4 weeks |
Off-the-shelf SaaS stays relevant for a small office of 2 to 3 people. Beyond 8 to 10 users, the monthly bill (8 users at EUR 90 = EUR 720 a month, EUR 8,640 a year) catches up with the annualised cost of an app you control, without the freedom on templates and export.
The export to the practice software is what moves the budget most: depending on whether the vendor offers an API, a file import or nothing at all, allow EUR 3,000 to 12,000 for this connector alone.
Expected gains on 60 reports a month
| Indicator | Before (paper + camera) | After the app | Difference |
|---|---|---|---|
| Re-entry time per report | 1 h 30 | 0 h 20 | 1 h 10 saved |
| Misfiled or lost photos | 3 to 5% | Under 0.5% | Divided by 6 |
| Time to deliver the report to the client | 5 to 8 days | 1 to 3 days | 4 days less |
| Disputes over attachment dates | Occasional | Almost none | Technical proof |
| Hours recovered per month | 0 | 70 | 70 h |
Mini case study
Illustrative scenario. Maître Laurent, partner bailiff in a 12-person office in Lyon, produces 60 reports a month. Each report needs 1 h 30 of re-entry by a clerk with a loaded cost of EUR 38 an hour. Current cost: 60 × 1.5 × 38 = EUR 3,420 a month.
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With the integrated version at EUR 42,000 excl. VAT, re-entry drops to 20 minutes: 60 × 0.33 × 38 = EUR 752 a month. Saving: EUR 2,668 a month. Subtract EUR 400 of timestamping and EUR 180 of hosting: net gain of about EUR 2,090 a month. Add annual maintenance (EUR 7,000, i.e. EUR 580 a month): net gain of EUR 1,510 a month, and a payback in 28 months on re-entry alone. If the 70 freed hours go into extra reports billed EUR 250 to 400, five more reports a month bring payback under 12 months.
FAQ
Is a photo timestamped by the app worth more than a regular smartphone photo?
Yes, because the qualified timestamp and SHA-256 hash prove the date and the absence of editing. A smartphone's EXIF metadata can be changed in seconds, whereas a qualified token costs EUR 0.05 to 0.30 and remains enforceable.
Does the app work without a network?
It must: reports in cellars, car parks or rural areas often represent 10 to 20% of jobs. Files are encrypted locally then timestamped on reconnection, with the capture time recorded in the audit log.
How long until a first usable version?
Allow 8 to 10 weeks for a field MVP at EUR 20,000-28,000 excl. VAT, tested by 2 or 3 officers. The version integrated with the practice software takes 14 to 20 weeks.
Where is the data stored?
On hosting in France or the European Union, encrypted, for EUR 80 to 250 a month. Retention of originals follows the deed retention period defined by the office.
Do we need both iOS and Android apps?
A cross-platform app (React Native or Flutter) covers both for only 10 to 15% extra, versus nearly double for two separate native apps.
Let's scope your project. Send us your report volume, practice software and report templates: we will price an MVP or an integrated version with an indicative budget and a realistic schedule. 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.
