API integration is the automatic exchange of data between two or more software systems through defined gateways called APIs (application programming interfaces). A web-shop order goes straight to the ERP, stock updates on both sides, the invoice reaches the e-invoicing provider and a courier is booked, with no one retyping data. Done well, it removes double entry and delays.
This guide explains how API integration works, which method to choose when, the connections businesses in Türkiye need most, and eight steps to a robust integration project.
Why API integration matters: disconnected systems in most companies
A typical mid-sized company runs several separate pieces of software side by side: an ERP or accounting package, a web shop or B2B dealer portal, one or more marketplace dashboards, an e-invoicing provider, the courier's booking screen and the bank's online portal. Each does its own job well. The problem is the gap between them. On the HR side, one of the most common links is time and attendance payroll integration, which moves timesheets into payroll.
People usually fill that gap. Someone in sales operations downloads marketplace orders into a spreadsheet and keys them into the ERP one by one; the warehouse updates stock on the web shop by hand at the end of the day; finance downloads the bank statement and matches receipts to customer accounts. During the day a product shown as in stock may already be sold, and an order marked "shipped" may still be sitting in the warehouse. The report a manager sees depends on which system it was pulled from.
What the lack of integration costs
A large share of Turkish businesses still lacks an integrated core system. According to the TurkStat ICT Usage in Enterprises Survey 2025, 28.3% of Turkish enterprises with 10+ employees used ERP software, 12.0% used CRM and only 6.5% used business intelligence (BI) software. That points to a lot of data still being moved by hand between spreadsheets, emails and standalone programs.
At the same time, the number of digital channels that need connecting keeps rising:
According to the TurkStat ICT Usage in Enterprises Survey 2026, the share of Turkish enterprises selling via the internet or EDI (electronic data interchange) rose from 13.6% in 2024 to 17.1% in 2025, reaching 29.7% among firms with 250+ employees.
The same is true of statutory documents. Türkiye requires many businesses to issue invoices and dispatch notes electronically through the Revenue Administration's systems (e-Fatura and e-İrsaliye). The Turkish Revenue Administration (GİB) 2025 Annual Activity Report shows the number of taxpayers using e-İrsaliye rising from 402,985 in 2024 to 632,288 at the end of 2025. Every new e-document obligation adds another data flow between the ERP and the provider.
When these flows run by hand, the cost shows up in three places: staff time (the same data entered several times), errors (wrong stock, wrong prices, missing invoices) and decision speed (managers acting on out-of-date figures). Bringing data from several systems together for reporting is the job of a data warehouse and ETL.
How API integration works, and which method to use when
Think of an API as a waiter in a restaurant. You do not walk into the kitchen (the system); you give the waiter (the API) a defined order and receive a defined response. The system owner decides through the API which data is exposed, to whom and with what permissions.
Not every integration is built the same way. The most common options:
| Method | How it works | Best suited to | Watch out for |
|---|---|---|---|
| REST API (request-response) | One system asks another to "return this order" or "save this record" | Record-based work: orders, accounts, stock | Rate limits and error handling |
| Webhook (event notification) | A system notifies another the moment something happens | New orders, payment confirmations, delivery status | Retrying missed notifications |
| Scheduled file transfer | CSV/XML files are moved at set times | Legacy systems without an API (for a lasting fix, see legacy software modernisation), bulk price lists | Latency — no intraday accuracy |
| EDI / standard documents | Parties exchange documents in an agreed standard format | Trading with large suppliers and retail chains (what EDI is) | Format compliance and testing |
| Screen automation (RPA) | A bot uses the screens a person uses | Systems with no API that cannot be changed | Maintenance when screens change |
For permanent, high-volume flows, APIs combined with webhooks give the most robust result. We explain when screen automation makes sense for systems without an API in what is RPA. When choosing new packaged software, always ask whether it offers a documented, versioned API; integration capability is one of the deciding criteria in the custom vs off-the-shelf software decision.
The integrations businesses in Türkiye most often need
- ERP ↔ web shop and marketplaces: orders flow into the ERP, and stock and prices are updated on every channel from a single source. See our marketplace integration and B2B ecommerce ERP integration guides for the detail.
- ERP ↔ e-Invoice / e-Archive / e-Dispatch provider: the document is created in the ERP, sent to the accredited provider and its status is returned. We cover this in detail in our e-invoice integration guide.
- ERP ↔ bank: account movements are fetched automatically and receipts matched to customer accounts. We cover the matching rules in bank reconciliation automation.
- Orders ↔ courier: shipments are booked automatically and the tracking number returns to the customer and the system. The same data can answer "where is my order?" through a WhatsApp business chatbot.
- CRM ↔ ERP: sales and finance see the same customer balance and order status. We cover the sales side in our CRM sales pipeline guide.
- Production and field systems ↔ ERP: shop-floor, warehouse and field data reach the ERP in real time, and vehicle location, mileage and fuel data can join the same flow through a fleet management system. The ISA-95 model that defines the layers between the shop floor and ERP, and where MES sits in that flow, is explained in MES vs ERP.
Why the ERP sits at the centre of all this is covered in our guide to ERP for SMEs. Sector-specific flows follow the same logic: hospital queue and appointment management, for example, links appointment data in the hospital information system to calling screens.
Eight steps to a robust integration project
- Decide who owns each piece of data. Choose one source of truth per data type: does the ERP own prices, or the web shop? Skip this decision and two systems will end up overwriting each other.
- Map the flows. Which event (new order, return, stock change) goes from which system to which, and how often? A one-page flow diagram is enough.
- Write down the field mapping. Product codes, units, VAT rates and account codes need to be matched on both sides in a table.
- Define errors and retries. What happens when the other system does not respond? Records should wait in a queue, be retried and, after a set number of attempts, be flagged to someone responsible.
- Prevent duplicates. Give every record a unique reference so the same order is never transferred twice. Cleaning up duplicates that already exist in source systems is a separate job, covered in data quality and duplicate records.
- Log and monitor. Every transfer — when it ran and with what result — should be visible, so "why didn't this order reach the ERP?" can be answered in minutes.
- Test real scenarios in a test environment. Returns, partial shipments, cancellations and price changes must be tested before go-live.
- Plan ownership and maintenance. Who updates the integration when the other side releases a new API version? The contract should answer that.
Guides to the systems integration connects, such as ERP, CRM, WMS and dealer portals, are collected in our Software Development articles.
Security: every integration is a new door
An API integration opens a new route for data to leave and enter the organisation. If it is unclear who uses that route and with what rights, the risk grows. According to the Verizon 2026 Data Breach Investigations Report, breaches involving a third party rose 60% in a year to 48% of all breaches.
The basic rules are simple. API keys never go into source code or emails; they live in a secure vault. Each integration accesses only the data it needs. Keys are rotated regularly, and access is revoked as soon as a partnership ends. Integrations that move personal data must also appear in your data inventory under KVKK, Türkiye's Personal Data Protection Law No. 6698.
In automotive supply chains the most demanding integration is message exchange with the vehicle maker; we cover DELFOR and DESADV flows separately in our automotive EDI integration guide.
How we deliver integrations at Digital Bridge
- We map your current systems. Through our API integration service we list the software you use, which systems expose APIs and where data is still moved by hand today.
- We choose the right method. A direct connection where an API exists; a scheduled transfer or screen automation where it does not. Hardware links — machines, terminals, sensors — are handled by the same team through our system integrations work, so there is no gap in responsibility between software and hardware.
- We design a single data flow. Where several systems must work together in one business process, we design the order, stock and invoice flow end to end with our integrated systems approach, and connect sales channels through e-commerce and B2B platforms. SmartSales, the e-commerce product in our Smart family, feeds the storefront, marketplaces and product feeds from a single catalogue; its headless API uses separate read and management tokens, and the management token writes only catalogue and stock data.
- We build security in from the start. Key management, permission boundaries and logging follow the principles of our cyber security consultancy.
- We bring emailed documents into the flow. Where supplier invoices arrive by email, SmartMail, part of the Smart360 suite, extracts fields such as totals, VAT, dates, document number and tax number from the attached invoice PDF without the file being downloaded, and the attachment can be saved to SmartFiles in one click.
- We make the result visible. Integrated data can feed a BI dashboard so management sees one version of the numbers.
Scope, phases and cost are set out in a written proposal; we do not push a packaged product.
To decide which process to integrate first, use the prioritisation matrix in our article on which business processes to automate first.
Next step
Start with a sheet of paper: list every piece of software your company uses and draw an arrow wherever data is moved between them by hand. The system with the most arrows shows where integration should begin. Bring that diagram and contact us — we will work out together which connection will pay back first.