How to Prepare Technical Requirements for a Custom Software Project

The purpose of a technical requirements document is not to produce hundreds of pages, but to reduce uncertainty between the product and development teams.

A good document clarifies what is out of scope as well as what will be built, and defines the criteria for accepting delivery.

Problem and objective

Before technical details, define the business problem to solve and the expected outcome.

User roles

Clearly specify which data each role can see and which actions it can perform.

Administrator
Operations user
Customer
Manager
Service account

Functional requirements

Describe user actions and system behaviour instead of saying “orders will be managed”. For example: “An operations user can filter new orders by date and status.”

Acceptance criteria

Convert every critical requirement into testable acceptance criteria. This reduces differences in interpretation between development and QA.

Non-functional requirements

Performance
Uptime
Security
Logging
Backup
Browser support
Accessibility

Integrations

Document API endpoints, authentication methods, rate limits, webhooks, data mapping and error conditions.

Data model

Identifying core entities and relationships early allows more accurate design of backend and reporting requirements.

Edge cases and failure scenarios

Define exceptions such as failed payments, API timeouts, duplicate requests and insufficient stock alongside the successful flow.

Out-of-scope areas

Explicitly identifying functions that will not be delivered in the first phase reduces scope-creep risk.

Putting project decisions into practice

Treat the problem and goal, user roles and functional requirements as parts of one decision chain. Clarify not only features but data sources, user roles, security boundaries, integration dependencies and success metrics. Convert these into a backlog, acceptance criteria and a technical risk list so progress can be tracked through measurable outputs rather than personal interpretations.

In enterprise software, a solution that works today is not necessarily sustainable long term. Include testable code, deployment, logging, monitoring, data migration and rollback capability in the initial architecture. This helps control rework and operating costs in later releases rather than simply slowing development.

Implementation checklist and technical risks

A feature list alone is not enough. Record decisions about the problem and goal, user roles and functional requirements at the start of technical design. For each critical requirement, define the responsible team, data source, expected behaviour, failure scenario and acceptance criterion. This reduces later scope disputes and gives product, software, operations and business teams a shared reference.

Assess integration dependencies, user permissions, data integrity, third-party outages and expected scale separately. For an external API, design for timeouts, rate limits, duplicate requests, data mismatches and temporary outages as well as successful responses. Audit logs, rollback or retries for critical operations help teams recover safely after errors.

Before launch, define measurable performance and security targets: operation durations, role-based data access, log retention and error tracking. After deployment, monitor application logs, errors, database performance, queue status and critical external latency. This helps detect issues without waiting solely for user complaints and supports managing software as a sustainable product, not a one-off project.

Matching functions to acceptance criteria
Authorisation and data access controls
API and integration failure scenarios
Backup and rollback approach
Monitoring and error tracking
Performance and capacity targets

B10 Digital Agency’s software approach

B10 Digital Agency treats custom software as digital product development, not just screen design. Process analysis, UX/UI, architecture, APIs, security, DevOps and measurement are designed together.

Frequently asked questions

Who should prepare the technical document?

The product owner, business unit and technical team should work together.

Can the document change after development starts?

Yes, but the effects of changes on scope and schedule must be recorded.

Is a user story enough?

It may be sufficient for simple features; complex integration and security requirements must be documented separately.

Why are acceptance criteria important?

They provide an objective way to measure whether a feature is actually complete.

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