The verdict in three sentences
For a Rotterdam architecture practice of 10 to 30 people, a custom tool for fee tracking by phase, time recording and invoicing costs €20,000 to €55,000 excluding VAT and takes 3 to 5 months. The right developer shows itself through its answers: it talks about SO, VO and DO phases, DNR 2011 terms, BIM links and accounting exports, not just frameworks. Ask the twelve questions below and reject any proposal that does not price monthly maintenance (€150 to €650) from day one.
Questions about the business and features
Dutch practices usually structure fees by the phases of the standard task description, from schetsontwerp (SO) through voorlopig ontwerp (VO), definitief ontwerp (DO), technisch ontwerp (TO) and construction support, often under DNR 2011 terms. These questions show whether a developer understands that logic.
| Question to ask | Good answer | Bad answer |
|---|---|---|
| How do you model fee allocation by phase? | A per project table with a percentage or fixed fee per phase, adjustable by change order | One amount field per project |
| How do you calculate billable progress? | Phase completion entered by the project lead and compared with hours used | Invoicing stays manual |
| How do staff record time? | Weekly timesheet by project and phase, desktop and mobile | Monthly spreadsheet import |
| How do you link to our BIM models? | Project and phase IDs aligned with the BIM model, issue links via BCF where useful | We do not touch BIM |
| Which accounting export do you offer? | Native export to your package, such as Exact Online or Twinfield, tested with your accountant | An Excel export will do |
| How do you flag overruns? | Alert when hours pass 80% of a phase budget | No alerts planned |
A developer who answers these six well has probably worked for engineering or professional services firms. If it hesitates on phases and change orders, plan two or three extra scoping workshops, about €1,500 to €3,000.
Questions about budget, timeline and contract
| Question to ask | Good answer | Bad answer |
|---|---|---|
| What is the total budget including maintenance? | €20,000 to €55,000 build plus €150 to €650 a month | We will discuss maintenance after launch |
| What is the detailed schedule? | 3 to 5 months in releases every 3 to 4 weeks | One final delivery date |
| How do you migrate live projects? | Import of active projects and unbilled fees | You will re-enter projects |
| Who owns the source code? | The practice, with IP assignment in the contract | We keep ownership |
| Where is data hosted? | In the EU, with a GDPR data processing agreement | No clear answer |
| How does acceptance testing work? | Two real projects run in parallel for two weeks | You test in production |
Budget benchmarks by practice size
The 2026 estimates below apply to practices in the Rotterdam region, excluding 21% VAT, and vary mostly with integrations and change order complexity.
| Practice size | Typical scope | Build budget | Timeline | Monthly maintenance |
|---|---|---|---|---|
| 10 staff | Time, phases, simple invoicing | €20,000 to €27,000 | 3 months | €150 to €250 |
| 15 staff | Plus overrun alerts and accounting export | €27,000 to €35,000 | 3 to 4 months | €250 to €380 |
| 20 staff | Plus BIM IDs and partner dashboards | €35,000 to €44,000 | 4 months | €380 to €500 |
| 30 staff | Plus multiple offices, mobile, client portal | €44,000 to €55,000 | 4 to 5 months | €500 to €650 |
Off the shelf practice management software, with plan based public pricing per user, is a valid alternative if your billing is standard. Custom makes sense when change orders, consortium projects or partner dashboards do not fit their screens.
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Illustrative example: Sanne, partner at an 18 person practice in Rotterdam, finds staff spend 1 hour a week re-keying time across three spreadsheets, 18 hours in total. At a loaded cost of €55 an hour, that is €990 a week, about €45,500 a year over 46 weeks. She signs a tool at €38,000 with €420 a month in maintenance, €5,040 a year. If re-keying time drops by two thirds, she recovers about €30,300 a year, so the project pays back in roughly 18 months, before counting phase fees that no longer slip through.
FAQ
What budget should a Rotterdam practice plan for custom software?
In 2026, plan €20,000 to €55,000 excluding VAT depending on size and integrations, plus €150 to €650 a month for maintenance. A 15 person practice often lands around €27,000 to €35,000.
How long does development take?
Three to five months, ideally in releases every 3 to 4 weeks. Add 2 weeks of parallel running on real projects before switching off spreadsheets.
Do we need to follow DNR 2011 phases exactly?
The tool should mirror the phases in your client contracts, which for most Dutch practices follow the standard task description. For smaller private clients, 4 or 5 simplified phases are often enough.
Can the tool replace our accounting package?
No, it feeds it: the tool produces invoices and an export, bookkeeping stays in Exact Online, Twinfield or similar. Have your accountant validate the export format before the end of the first release.
Is there a cheaper option than €20,000?
Kolonell builds medium complexity web applications for 2,500,000 to 4,000,000 FCFA (about €3,800 to €6,100) in 2 to 3 months, managed remotely. It is worth benchmarking, provided scoping workshops fit your time zone.
Let's scope your project. Tell us your phases, headcount and accounting package, and we will price your fee tracking tool from 2,500,000 to 4,000,000 FCFA (about €3,800 to €6,100), delivered in 2 to 3 months. 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.
