- Custom software
- Fixed price in 3 days
- First slice in 2 weeks
Software for the work
your tools do not cover.
Built around how your business actually works. The code is yours from the first commit.
You talk to the engineer who builds it.
12products shipped
7 built solo, 5 embedded in client teams.
What I build.Where off-the-shelf stops.
- 01
Internal tools
The spreadsheet your team runs on, rebuilt with roles, an audit log and an export.
- 02
Customer portals
A login per customer, their orders and invoices, and an assistant that answers only from their data.
- 03
Integration layers
The piece between systems that do not talk, with a log of what ran and what it did.
- 04
Legacy modernization
Old software pinned down with tests, then replaced module by module, not in one risky rewrite.
- 05
Compliance layers
E-invoicing, AI disclosure and the audit trails your auditors ask for.
- 06
AI where it earns its place
Extraction, classification and search over your own data, wherever they remove work.
Read moreintegration layers vs automation platformsmodernizing a legacy application
Call to launch.In weeks, not quarters.
Start with the callErgini · Software & AI developer
I build every project myself,so I only take a few at a time.

3 days
A fixed price, in writing,
three days after the call.
- Scoped from what we discuss on the call.
- Agreed before any work starts.
Builds like these.Worked examples, end to end.
All use casesAn e-invoice layer that lets an old ERP issue XRechnung and ZUGFeRD before 2027
Reads invoice data from the ERP you already have, maps it to EN 16931, generates XRechnung or ZUGFeRD, validates every file with KoSIT and sends it by email or Peppol.
The existing ERP or billing system / KoSIT validator / Email (Outlook or plain SMTP)
Turning a 40-tab dispatch spreadsheet into an internal tool with rules, roles and history
Moves daily planning off a 40-tab spreadsheet into a web tool with validated forms, roles and a full edit history, while people keep Excel for analysis.
Excel and Google Sheets / Postgres / Microsoft 365 single sign-on
A customer portal where B2B clients track orders, download documents and ask questions
Each customer company gets its own logins, live orders and shipments from the ERP and carriers, every document in one place, and an assistant that sees only their data.
NetSuite / SAP Business One / Carrier APIs or the TMS
Questions.Answered straight.
What counts as custom software here?
Software built around how your business actually works, usually because no product on the market fits: internal tools that replace spreadsheets, portals for your customers or partners, integration layers between systems you already run, and modernized versions of legacy applications. New products for founders are covered by MVP Development.
Should we buy a SaaS product instead?
Often, yes, and I will say so on the call. If a standard product covers the process with configuration, buying it is cheaper and faster than any build. Custom software earns its cost when the process is a genuine advantage, when it spans systems no product connects, or when the product you would buy forces the team to work around it.
Who owns the code?
You do, from the first commit. It lives in your repository, runs in your accounts, and the credentials are in your name. Handover includes documentation and a recorded walkthrough, so another engineer can pick it up. There is no lock-in and no proprietary framework underneath.
How long does an internal tool take to build?
A contained internal tool, such as one workflow with forms, roles, an audit log and an export, is typically a few weeks. A first working slice reaches your team within the first two weeks so they can use it on real data, and the rest is built in weekly increments against their feedback.
Can it work with the systems we already use?
That is usually the point. Most builds read from and write to an ERP, a CRM, an accounting system or a database you already run, through their APIs where they exist and through exports, database connections or supervised browser automation where they do not.
What does custom software development cost?
It depends on scope, and you get a fixed price in writing within three days of the call, before any work starts. Custom software runs from a small internal tool to the replacement of a core system, so it is never priced from a table; a contained internal tool typically takes a few weeks. A new product follows MVP Development.
Pick a time.The call is free.
30 minutes, on Google Meet
Prefer email? ergin@ergini.com. I reply within hours.