Written by
Prachi Gupta
Published
November 5, 2025
2
min read

Build vs. Buy for FP&A forecasting: Key considerations before you decide

Before deciding whether to build a forecasting solution internally or adopt a ready-made platform, finance and IT leaders should pause to ask a few fundamental questions.
These questions clarify not only cost and effort — but also focus, agility, and long-term sustainability.

Questions to Ask Before You Decide to Build or Buy

1. Is there already a tool or platform that solves this problem effectively?

If a proven solution exists and can be configured to your needs, replicating it internally often brings limited additional value. Reinventing existing capabilities rarely delivers a better return on investment.

2. Will building this internally create a sustainable competitive advantage?

A good litmus test: if the capability isn’t central to your company’s core business or intellectual property, it’s often better to buy.
Build where you differentiate — buy where you can standardize.

3. Is it faster to build than to buy and implement?

Consider time to value, not just time to prototype. Include testing, rollout, change management, and user adoption in your timeline.

4. Do we have the right internal expertise to build and maintain it?

AI forecasting demands finance domain knowledge, ML expertise, and secure data architecture. Missing any one of these extends timelines and increases delivery risk.

5. Can we sustain long-term maintenance and updates?

Internal builds come with ongoing technical debt, retraining needs, and dependency on specific engineers or data owners.
If the original builders move on, continuity can become a serious challenge.

The Hidden Costs of Building In-House

While building an internal forecasting platform may appear cost-efficient at first glance, the total cost of ownership tells a different story.
The initial development investment is only the beginning — most of the expense comes later, through maintenance, model retraining, and the technical debt that accumulates as systems evolve.

1. Cost of Ownership

The financial outlay for a custom forecasting solution extends well beyond the first release:

  • Ongoing maintenance: Continuous updates are needed to reflect new cost structures, departments, and business drivers.

  • Data integration upkeep: Each change in source systems (HRIS, ERP, recruiting) requires developer intervention.

  • Testing and validation: Every forecasting cycle demands regression testing to ensure models still behave as expected.

Over a three- to five-year horizon, these recurring expenses often exceed the original build cost.
Industry studies show that maintenance alone can consume 40–60 % of total software spend over a product’s lifecycle.

2. Technical Debt

When engineering resources rotate or priorities shift, documentation and model ownership often lag behind.
This creates technical debt — the accumulated complexity of code, workflows, and assumptions that become harder to untangle over time.

Common symptoms include:

  • Delays in implementing even minor changes

  • Dependency on a few engineers who understand the system’s history

  • Risk of model drift as business logic evolves faster than code updates

The longer the system runs, the higher the maintenance overhead and the greater the risk that forecasts lose accuracy or traceability.

3. Lack of Finance Domain Expertise

Perhaps the most overlooked cost is context.
IT and data teams bring strong technical capabilities but are not finance practitioners.
They may not instinctively understand the nuances of headcount capitalization, deferred expenses, or period-end adjustments.

As a result:

  • Forecasting models can miss key accounting drivers or treat one-time events as recurring spend.

  • Data validation rules may not align with finance’s reconciliation standards.

  • Business users lose confidence in model outputs, forcing finance to re-work results manually.

Bridging this gap requires constant collaboration between finance and engineering — an ongoing coordination cost that can strain already limited resources.

4. Heavy Reliance on IT

Even when the system works, the operating model behind it often doesn’t.
Because IT teams control data pipelines, access permissions, and model deployment, finance must depend on them for every enhancement or correction.

That dependency creates a bottleneck:

  • Small logic changes can take weeks to deploy

  • Forecast refresh cycles slow down when IT priorities shift

  • Finance loses agility to respond to business changes in real time

Instead of empowering finance, internal builds can unintentionally centralize control within IT — reducing the flexibility that modern forecasting demands.

What Industry Research Says

Independent research by McKinsey, Bain, and Gartner has found that organizations routinely underestimate the demands of building internal systems.
Across industries, companies misjudge:

  • Maintenance effort by 40–60 %

  • Time to value by 2–3× versus expectations

  • Specialist skill requirements needed to sustain model accuracy and compliance

In other words, the challenge isn’t just building — it’s maintaining.
Finance teams often underestimate the engineering dependency required to keep internally built tools relevant as data, models, and business assumptions evolve.

What Leaders Have Said

“Anything we build will have a maintenance cost in the future that has to be considered. Moreover, the software you are ‘going to build’ always looks better than the software someone else already has—until you hit the limitations.”
Timothy Campos, CIO, Facebook

“Everybody knows that the more you buy off-the-shelf, the more cost-effective it will be for both implementation and ongoing maintenance.”
Mark Lutchen, Former Global CIO, PwC

These reflections highlight that building and buying are not purely financial decisions — they’re strategic capacity decisions.

Comparative Snapshot

Criteria Build In-House Buy (Established Platform)
Time to Value Months to usable output Weeks to pilot
Cost of Ownership High + continuous maintenance Lower, predictable subscription
Maintenance Fully internal Vendor-managed
Domain Expertise Must be built in Embedded
Security & Compliance Custom framework maintained internally Vendor-managed, audited controls (enterprise standards)
Sustainability Depends on staff continuity Independent of turnover

Making the Decision

There’s no one-size-fits-all answer.
But a few guiding questions can help clarify the right path:

  • How quickly do we need to demonstrate results?

  • Do we have the engineering bandwidth to maintain what we build?

  • How sensitive is our data, and what governance standards must be met?

  • Where do we want our finance and IT teams focused — building infrastructure or driving strategic insight?

For many finance organizations, the optimal path blends both: build for what’s unique, buy for what’s repeatable.

The Bottom Line

The build vs. buy question isn’t about ownership — it’s about capacity.
In a world where AI models, compliance standards, and data pipelines evolve rapidly, the real differentiator is how fast finance can act on reliable forecasts.

Choosing a platform with mature, vendor-managed security and compliance can often deliver both speed and peace of mind — letting finance leaders focus on outcomes, not infrastructure.

Not sure which path is right for your team? Let’s explore your current setup and see where AI forecasting can accelerate value without a long implementation cycle.

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