Integration Requirements: Writing a BRD and SRD for Finance System Integration
Lightbridge ERP defines integration requirements as the documented agreement of what a finance system integration must do and how it must do it. Two documents carry it: a business requirements document (BRD) states the business need, scope, and success criteria, and a solution requirements document (SRD) translates that need into the technical specifications a delivery team can build and test against.
This guide is general information, not accounting, tax, or legal advice. Lightbridge ERP leads the requirements and finance-data design; the integration platforms are delivered by Lightbridge Cloud.
Requirements documents decide a finance integration before any code is written.
Most finance system integrations do not fail in the build. They fail in the requirements. PMI's Pulse of the Profession found that inaccurate requirements gathering was a primary cause of project failure for 37% of organizations, up from 32% the year before. A requirements document is the deliberate countermeasure: it forces finance, IT, and operations to agree on what the integration must do, and on how success will be measured, before anyone commits effort to building it.
Two documents do the work. The business requirements document (BRD) is the agreement on the need: scope, objectives, processes, and success criteria, written for the business. The solution requirements document (SRD) is the blueprint for the need: architecture, integration specifications, data mapping, and testing, written for the delivery team. This guide is the companion to the broader ERP integration overview and to the integration strategy guide; requirements are what turn a chosen strategy into a buildable, testable plan, the integration project management guide covers how the program that delivers them is run, and the reporting integration guide covers designing the flows that feed reporting and BI.
BRD versus SRD: what the business needs, then how the solution delivers it.
The BRD and the SRD are not rivals or duplicates. They are sequential layers of the same agreement. The BRD answers what and why; the SRD answers how. Confusing the two is a common requirements mistake: a BRD that drifts into technical design locks in implementation choices too early, and an SRD with no BRD behind it builds a precise solution to an unagreed problem.
Question it answers
BRD
What the business needs, and why
SRD
How the solution will deliver it, technically
Level of detail
BRD
High-level, business-oriented
SRD
Detailed, technically specified
Primary audience
BRD
Business stakeholders, finance, sponsors
SRD
Architects, developers, QA, project managers
Typical content
BRD
Objectives, scope, processes, functional and non-functional requirements, success criteria
SRD
Architecture, system and integration requirements, data mapping, security, performance, testing, traceability
When it is written
BRD
First, to define and align the need
SRD
After, to design against the agreed need
What a business requirements document (BRD) contains.
A BRD for a finance system integration is a contract between the sponsoring business and the project team. It compiles everything gathered from stakeholders into one reviewed, agreed document. The sections below are the recurring components; the discipline is that each requirement is specific, measurable, and traceable to a business objective.
Executive summary and background
A short overview a sponsor can read in a minute: what the integration is, the main objectives, the expected outcomes, and the context that makes it necessary. The background explains the current situation and the problem or opportunity the project addresses.
Business objectives and scope
Specific, measurable objectives stated as outcomes, not features, paired with an explicit scope: which systems and processes are in, which data flows are covered, and what is deliberately out of scope. A clear in-and-out boundary is the single best defense against scope creep.
Stakeholder and current-state analysis
Who is affected, their interest and influence, and how each is kept informed; alongside an honest read of today: the current systems, the process as it actually runs, the pain points, and the metrics (processing time, error rate) the project intends to move.
Process, workflow, and triggers
The business process broken into discrete steps with defined inputs and outputs, a plain-language description of what each workflow must achieve, the applications involved, and what makes the workflow run: an event (a record created or changed) or a schedule (a nightly sync).
Data rules and exception handling
How time-sensitive the data is and how often it must move, which records qualify for processing, the validation rules and business logic applied in transit, and what happens when something goes wrong: a credit limit exceeded, a record out of stock, a mismatch between systems.
Functional and non-functional requirements
Functional requirements state the specific, testable things the integration must do from a business view. Non-functional requirements state the quality attributes it must hold to: performance, availability, scalability, security, and usability, expressed as targets the result can be measured against.
Assumptions, constraints, and success criteria
The assumptions the plan rests on, the known constraints (timeline, budget, existing licenses, no new hardware), and the measurable criteria that decide whether the project succeeded. Each requirement should trace back to a stated business objective.
What a solution requirements document (SRD) contains.
The SRD takes the agreed business requirements and turns them into a technical blueprint precise enough to build, estimate, and test against. Where the BRD describes the business outcome, the SRD specifies the systems, interfaces, data, and controls that produce it. Each component below maps back to the need the BRD recorded.
Solution overview and architecture
A high-level description of the proposed solution: the overall architecture, the key components and how they interact, the integration patterns used, and the data-flow diagrams. This is where the agreed business need first takes a technical shape.
Technical and integration requirements
The system, platform, and deployment requirements (environments, runtime nodes, monitoring, CI and CD), and the specific integration points: the interfaces used, the data formats, the communication protocols, and the error-handling and retry behavior between systems.
Functional specifications
The high-level functional requirements from the BRD expanded into precise, testable specifications, organized by business process or module. Each one names the trigger, the action, and the timing, so a developer can build it and a tester can verify it.
Data requirements
The data elements exchanged and the transformations needed: field-level mapping between systems, validation rules, format standardization, and the expected volumes and frequency of exchange. For finance, this is where the authoritative-record decisions become explicit.
Security and performance requirements
Encryption in transit and at rest, authentication and authorization, audit logging and retention, and compliance obligations; alongside the performance envelope: response-time and throughput targets, scalability expectations, and availability and reliability commitments.
Testing and deployment
The testing approach (unit, integration, user acceptance, and performance), the deployment strategy (phased rollout with a rollback plan, rather than a single cut-over), and the monitoring, backup, and disaster-recovery requirements that keep the integration dependable in production.
Traceability matrix
A matrix that links every technical requirement in the SRD back to a business requirement in the BRD. It is the proof that the solution addresses the actual need and the mechanism that keeps a project anchored to business value as scope and detail grow.
The technical platforms an SRD specifies (iPaaS, API gateways, message queues, and streaming pipelines) are owned, built, and operated by Lightbridge Cloud. Lightbridge ERP writes the requirements and designs the finance-data side: which system is authoritative for each record, how fields map, and where reconciliation and the audit trail live.
Traceability is what keeps requirements honest from BRD to delivery.
The link that holds the two documents together is the traceability matrix: every technical requirement in the SRD points back to a business requirement in the BRD, and every business requirement points forward to the test that proves it. That single discipline is what prevents the two most expensive requirements failures, a solution that is well built but solves the wrong problem, and a business need that quietly never gets delivered. Both documents stay living: they are revised as the project reveals what the early gather could not see.
For finance specifically, the requirements stage is where the governance decisions are made on purpose rather than by accident. One system has to be authoritative for each record, the audit trail has to survive every hand-off, and reconciliation has to be a system task rather than a spreadsheet. Because Lightbridge ERP is staffed by senior finance professionals, the requirements are written around how the books actually reconcile. Lightbridge ERP operates to ISO 27001 and SOC 2 controls, with certification in progress. To justify the program the requirements describe, see the ERP integration business case.
AI raises the bar on requirements; it does not lower it.
As finance integrations move toward real-time, event-driven, and agentic designs, the requirements have to be sharper, not looser. An automated process acting across systems needs the same authoritative master data, audit trail, and reconciliation contracts a human-run process does, and those obligations have to be written into the BRD and SRD before an agent is allowed to act on them. The non-functional requirements (latency, data quality, lineage, and observability) become the controls that make an AI-assisted close auditable rather than a new source of unexplained numbers. Generative-AI strategy and AI governance are owned by Lightbridge Labs; see also AI in ERP.
Integration requirements (BRD and SRD): frequently asked questions
- What is a business requirements document (BRD)?
- A business requirements document (BRD) is a formal statement of what a project must achieve for the business and why. For a finance system integration, it defines the objectives, the scope (which systems and data flows are in and out), the affected processes, the functional and non-functional requirements, and the measurable criteria for success. It is written for business stakeholders and sponsors, stays focused on the need rather than the technical implementation, and serves as the base document the rest of the project is built and measured against.
- What is the difference between a BRD and an SRD?
- A BRD answers what the business needs and why; a solution requirements document (SRD) answers how the solution will deliver it, technically. The BRD is high-level and business-oriented and is written first to define and align the need. The SRD is detailed and technically specified and is written after, expanding the agreed business requirements into architecture, system and integration specifications, data mapping, security, performance, and testing. The two are complementary: the SRD builds on the BRD, and a traceability matrix links every technical requirement back to a business one.
- Why do finance system integration projects need a requirements document?
- Because inaccurate requirements are one of the most common reasons integration and technology projects fail. A clear BRD aligns finance, IT, and operations on the same goals before any building starts, surfaces constraints and exceptions early, and gives the project a benchmark for success. For finance specifically, the requirements stage is where the authoritative-record, audit-trail, and reconciliation decisions get made deliberately rather than discovered late. Skipping or rushing it is what produces an integration that moves data but does not keep the books reconcilable.
- What goes into the requirements document for a finance integration?
- A BRD covers the executive summary and background, business objectives and scope, stakeholder and current-state analysis, the process steps and workflows, data sync frequency and processing rules, validation logic and exception handling, functional and non-functional requirements, and assumptions, constraints, and success criteria. The SRD then adds the solution architecture, technical and integration requirements, functional specifications, data mapping, security and performance requirements, the testing and deployment approach, and a traceability matrix back to the BRD.
- Who writes the BRD and SRD?
- The BRD is typically led by a business analyst working closely with the finance and operations stakeholders who own the process, with the project sponsor accountable for sign-off. The SRD is led by a solutions architect or technical lead who translates the agreed business requirements into a buildable design, reviewed by the development and QA teams. On a Lightbridge ERP engagement, senior finance professionals (CPAs, controllers, and former CFOs) shape the requirements so the integration is designed around how the books actually have to reconcile, not just how the data moves.
- How detailed should the requirements be before implementation starts?
- Detailed enough that each requirement is specific, measurable, and testable, and that every technical requirement in the SRD traces to a business requirement in the BRD. Requirements should prioritize must-haves over nice-to-haves, document assumptions and constraints plainly, and avoid prescribing implementation in the BRD (that belongs in the SRD). Both documents are living: they are revised as the project reveals new information. The goal is not exhaustive volume but unambiguous, traceable, agreed requirements that reduce rework once development begins.
- Does Lightbridge ERP write the requirements, or build the integration?
- Lightbridge ERP leads the requirements and the finance-data design: the objectives, scope, authoritative-record decisions, field mapping, and the reconciliation and audit-trail rules that the BRD and SRD record. The integration-platform delivery, the iPaaS, API, and streaming tooling that move the data, is owned and built by Lightbridge Cloud. Lightbridge ERP is an independent, vendor-neutral advisory firm that accepts no vendor kickbacks or reseller quotas, so the requirements follow business fit rather than a platform a reseller is incentivized to sell.
Get the requirements right before the build.
Lightbridge ERP writes the BRD and SRD for finance system integration vendor-neutral: agreed objectives, one source of truth, an intact audit trail, and traceable requirements the delivery team can build and test against.