Building an intelligent document processing (IDP) system in-house might seem appealing. You get control, flexibility and the ability to shape the system around your own architecture and data flows. But in reality, IDP building is rarely a one-time project. It’s an ongoing, resource-heavy commitment that grows more complex over time.
From accuracy ceilings to mounting maintenance demands, in-house builds often derail even well-resourced teams, pulling focus away from core initiatives.
This article breaks down five hidden costs of a build-your-own IDP system.
Cost 1: The last 5% is the hardest
Many teams start IDP building projects confident they can achieve high accuracy with LLMs. They know their business and what it needs, so how hard can it be? At first, hitting 90 to 95% accuracy feels like a win. But in practice, this is where progress stalls, and where automation goals begin to crumble.
The remaining 5% is the toughest to solve. Edge cases, inconsistent formatting and complex document types create errors that compound over thousands of files. Without years of data, domain expertise and iterative model tuning, most in-house builds never achieve the straight-through processing they aim for, despite the best efforts of the people working on them.
Commercial-grade vendors have invested a decade in solving these last-mile challenges, reaching the accuracy thresholds that make automation truly scalable.
Cost 2: Building IDP takes focus away from core projects
On paper, IDP building seems like a great way to leverage your in-house talent and save costs. But every hour your engineering team spends designing, testing and debugging an IDP system is an hour not spent on core, customer-facing or revenue-driving initiatives.
IDP isn’t a once-off project. It requires ongoing maintenance, refining and defining fields, tuning for accuracy and adapting to evolving document formats. Even highly skilled teams can find themselves buried under long-tail technical debt, turning what should have been a quick build into a permanent side project.
Specialist vendors free up your team’s capacity, allowing them to focus on the innovations that differentiate your business, not the heavy lifting of document processing infrastructure.
Cost 3: The never-ending project of continuous improvement
Many teams think IDP building is a one-off investment: develop the system and it’s set to manage your document processing for years to come. In reality, semi-structured and variable document types, such as invoices, IDs, payslips, financial statements and onboarding documents, evolve constantly.
When you build your own IDP on top of LLMs, every new edge case adds complexity. Instead of retraining models, teams end up constantly adjusting prompts, adding special-case rules and rebuilding orchestration flows. Each change can have unintended side effects elsewhere in the workflow. What began as a finite project quickly becomes a permanent engineering commitment, draining time and resources.
This is where the build or buy IDP decision matters most. With Affinda, you’re not just getting an IDP tool, you’re getting a platform that keeps improving. Our data science team continually tests and strengthens the pipeline, and because we’re model agnostic, we can use the best available LLMs at each stage to maximise accuracy.
On top of that, your own models get smarter through everyday use. Instant learning and retrieval-based grounding allow your bespoke models to evolve with your documents, without engineering effort or ongoing optimisation on your side.
Cost 4: DIY builds struggle to scale
Connecting an in-house IDP to your wider tech stack is rarely simple. Teams need the technical capability to design and maintain custom integrations, and even small changes to upstream or downstream systems can require additional engineering work to keep everything running smoothly.
Scaling a DIY solution adds another layer of complexity. What works for one document type or workflow often doesn’t translate cleanly to others. Results can vary across formats, teams or regions, and maintaining consistency becomes an ongoing challenge as use cases expand.
When you build your own IDP, you own the entire integration burden forever. In contrast, mature vendors offer REST APIs, pre-built connectors and tools like Affinda’s Integrations Agent, which lets both technical and non-technical users configure custom connectors without writing code. This makes integrations faster, more reliable and easier to maintain as your business and needs grow.
Choosing whether to build or buy an IDP system isn’t just about core functionality; it’s about how seamlessly the solution works with the ecosystem you already have.
Cost 5: Long-term technical and financial debt
The true cost of IDP building isn’t just the initial development effort; it’s the ongoing debt you take on by committing to maintain and scale your own platform. Internal builds rarely reach commercial-grade straight-through processing without massive, ongoing investment in tuning, updates and feature enhancements.
When you build your own IDP, your engineering team becomes responsible for every new document type, every edge case, every compliance change. Over time, these hidden costs snowball, turning what looked like a cost-saving move into a permanent, expensive engineering obligation.
The IDP build or buy decision comes down to focus and efficiency. Buying from a specialist vendor transfers this long-term burden to experts who’ve already solved these challenges and can deliver accuracy, scalability and reliability without tying up your team or budget indefinitely.
Make the right build vs buy decision with confidence
Download our free whitepaper for a clear framework to compare building your own IDP system versus buying a platform. See the trade-offs in accuracy, scaling, integration effort and long-term maintenance so you can choose the best path for your team.
Focus on what you do best, and we’ll take care of IDP building
The idea of building your own IDP system can be tempting. On the surface, it promises control, cost savings and a tailor-made solution. But as these hidden costs show, IDP building is a long-term commitment that drains engineering capacity, racks up technical debt and often fails to deliver what your business needs.
If document processing isn’t your core business, it’s worth asking whether your time is better spent elsewhere. The smarter choice in the build or buy IDP debate is to partner with a specialist who has already solved the hard problems.
Affinda’s intelligent document processing platform delivers enterprise-grade precision without the long-tail costs of going it alone, plus we get you up and running fast, so you see value sooner. Start your free trial today and see how fast you can unlock reliable automation without the burden of in-house development
