Custom software for government agencies: what to know

Building software for a government agency is not just building software with more paperwork. The constraints are structurally different: accessibility is a legal requirement, security is audited, the users often cannot be turned away for a competitor, and the buying process can take longer than the build itself. Teams that treat a public-sector project like a commercial one tend to discover these differences late and expensively. This is what to plan for from the start.

Unique constraints in the public sector

The first thing that changes is who the users are. A government system frequently serves the entire public, which means it has to work for people on old devices, slow connections, assistive technology, and every level of digital comfort. You cannot design for a narrow, tech-savvy segment and let the rest churn out. There is no churn. There is only a citizen who still needs the service.

The second change is accountability. Public spending is scrutinized, records are often subject to open-records requirements, and decisions have to be defensible after the fact. That pushes toward thorough documentation, clear audit trails, and systems whose behavior can be explained, not just observed. Building for that from day one is very different from bolting it on later.

The third is longevity. Government systems tend to run for a long time. The GAO's 2025 review of critical federal legacy systems found systems ranging from about 8 to 51 years old, so the choices you make about maintainability and ownership matter more than in a product you might rewrite in three years. That makes owning the source code and the full runbook essential rather than nice-to-have.

Security, accessibility, and compliance

Three requirements sit at the center of nearly every public-sector build.

Security is non-negotiable and usually formalized. Depending on the agency and data, that can mean specific control frameworks, continuous monitoring, encryption in transit and at rest, strict access controls, and audited logging. The risk is not abstract: of the 11 critical systems GAO flagged, seven were operating with known cybersecurity vulnerabilities. A security-first posture, the kind that supports SOC 2 style controls, is the baseline, not a premium add-on. The same rigor that protects SaaS security and compliance applies here, often with additional government-specific frameworks layered on top.

Accessibility is a legal obligation, commonly anchored to WCAG and Section 508 style standards. This shapes the front end from the first wireframe: semantic markup, keyboard navigation, screen-reader support, sufficient contrast, and forms that anyone can complete. Retrofitting accessibility after the interface is built is slow and costly. Designing for it from the start is neither.

Compliance also touches data handling and residency. Where data lives, who can access it, and how long it is retained are often prescribed. A team fluent in US compliance expectations plans the architecture around these rules instead of discovering them during an audit.

Common government use cases

Public-sector software spans a wide range, but several patterns show up repeatedly:

• Citizen-facing portals for applications, permits, licensing, and payments.
• Case management systems that route work across departments with full audit history.
• Inspection, licensing, and field-service tools used by staff on the move.
• Data and reporting platforms that turn siloed records into oversight and transparency.
• Integrations that connect aging core systems to modern services.

This is a large and growing market, not a niche. State and local governments already spend more than $103 billion a year on IT, a figure the Center for Digital Government projected to exceed $153.6 billion in 2025, up 6.4 percent over 2024. The state and local government software market alone reached $9.7 billion in 2024, with the top 10 vendors holding 45.1 percent of it. Many of these projects overlap with commercial patterns Kadmoon builds every day: portals, workflow systems, integrations, and data platforms. The difference is the constraint envelope around them. If field staff are involved, the same principles behind field service mobile apps apply, with offline capability and rugged usability weighing even heavier for inspectors and agents working outside connectivity.

Legacy modernization needs

A large share of government software work is not greenfield. It is modernizing systems that have run for decades, sometimes on mainframes, often in languages few current engineers know. Both of the Treasury systems on GAO's critical list run on COBOL and Assembly Language Code, languages with a dwindling pool of people who can support them. These systems still work, which is precisely why they are risky: they are load-bearing, poorly documented, and understood by a shrinking group of people.

The money problem compounds the skills problem. The federal government spends more than $100 billion a year on IT, and agencies typically report that about 80 percent of it goes to operating and maintaining existing systems rather than modernizing them. The 11 legacy systems GAO singled out cost roughly $337 million a year just to keep running. Every dollar spent nursing old code is a dollar not spent replacing it, which is how a system reaches 51 years of age.

Modernization here is rarely a clean rewrite. The safer path is usually incremental: wrap the legacy system with APIs, move functionality piece by piece, and keep the old and new running side by side until the transition is complete. That approach reduces the chance of a catastrophic cutover on a system citizens depend on. Our guides on how to modernize legacy software and cloud migration strategy lay out the frameworks, and they map cleanly onto public-sector risk tolerance.

The ownership angle matters most here. When you modernize a system meant to run for another decade or two, you need to own the code, the pipelines, and the documentation outright. A dependency on a single vendor for a critical public system is a risk in itself.

Procurement and delivery realities

The part that catches commercial buyers off guard is procurement. Government purchasing runs through formal processes: solicitations, structured evaluations, and rules designed for fairness and auditability rather than speed. The timeline from need to signed contract can be long, and the requirements are often fixed in a document before a vendor is even selected.

That has two implications for delivery. First, the requirements you write up front carry more weight, so getting them right matters. A clear, well-structured requirements document is worth the effort. Second, even inside a rigid contract, iterative delivery still reduces risk. Two-week sprints with a working demo every cycle give stakeholders something concrete to react to, catch misunderstandings early, and produce the evidence trail that oversight expects. Measurable acceptance criteria written into the contract keep everyone aligned on what "done" means.

Delivery discipline also protects the agency's budget, and the track record for undisciplined public IT is poor. Federal modernization moves slowly even when it is planned: as of early 2025, agencies had completed only three of the ten modernizations GAO identified back in 2019, with several still years from a completion date and one with no plan at all. That pace is what happens when large scope, rigid contracts, and big-bang ambition collide. Phased work with acceptance gates is the counterweight. Spend is tied to results, each milestone is small enough to actually finish, and the agency keeps a working system at every step rather than betting years of budget on a single cutover.

Building for the public sector

If you are commissioning government software, a few principles keep projects out of trouble. Insist on full ownership of the source code, credentials, and runbook, because these systems outlive vendor relationships and, as the GAO data shows, some outlive the careers of the people who built them. Treat accessibility and security as first-class requirements designed in from the start, not features to be added later. Prefer incremental modernization over risky big-bang rewrites. And choose a delivery model with frequent, visible checkpoints so problems surface while they are still cheap to fix.

A senior in-house team, working in short sprints with contractual acceptance criteria and a security-first posture, fits the public-sector profile well. If you want to see how that approach maps to your agency's specific constraints, you can start a project or review how to choose a software partner before you write your solicitation.