Build a Production-Grade Accounts Payable Workflow
Custom Python automation provides unlimited conditional logic for complex approval chains. It connects directly to any financial API without relying on pre-built connectors.
Key Takeaways
- Custom Python automation provides unlimited conditional logic for complex financial approval chains.
- Direct API integrations connect to any vendor portal or accounting system, not just those with pre-built connectors.
- The system runs on your infrastructure, giving you full control over security, data residency, and processing logic.
- For our own operations, we built a system that syncs bank data via Plaid in under 3 seconds.
Syntora builds custom accounts payable automation for finance teams using Python and FastAPI. For its own operations, Syntora built a financial integration system that syncs bank transactions in under 3 seconds. The custom AP system provides a complete audit trail in a PostgreSQL ledger and eliminates manual data entry.
Syntora built financial APIs connecting Plaid, Stripe, and a custom PostgreSQL ledger for automated transaction categorization and tax estimates. For a custom accounts payable system, the scope depends on the number of vendors, the complexity of your approval rules, and which accounting software it needs to sync with.
Why Do Finance Teams Struggle with Multi-Step Invoice Approvals?
Many finance teams start with platforms like Bill.com for invoice management. These tools work well for standard single-approver workflows but break down when faced with complexity. For instance, an invoice over $5,000 might need approval from a department head, but only if it is for marketing spend and not if it is a recurring software subscription. Bill.com's rules engine cannot handle these nested, multi-variable conditions.
Consider a 20-person professional services firm. An invoice arrives from a new subcontractor for $7,500. The workflow should be: check if the PO number is valid in their project management tool, confirm the project manager approved the hours, then route it to the managing partner for sign-off. Point-and-click automation tools lack the ability to query the project management database directly to perform the PO validation. The AP clerk must manually check the other system, export a PDF, and email the partner for approval, which defeats the purpose of automation.
The structural problem is that off-the-shelf AP tools are built on a one-size-fits-all data model. They assume invoices have a fixed set of fields and approvals follow a linear path. Their architecture cannot incorporate external business logic, like checking a project budget before approving payment. This design prioritizes mass-market simplicity over the specific rules that allow a business to control costs effectively.
The result is a workflow filled with manual exceptions. This leads to late payments, missed early payment discounts, and hours of low-value work for the AP team chasing approvals. The lack of a central audit trail for these manual steps also creates compliance risks during financial reviews.
How Syntora Builds a Custom Accounts Payable System with Python
Syntora begins with a workflow audit. We map every step of your current AP process, from invoice receipt to final payment confirmation in your general ledger. This involves identifying every rule, exception, and approval threshold. The outcome is a detailed process diagram and a technical specification that you approve before any code is written.
The core of the system is a Python service built with FastAPI, which handles complex, stateful approval logic efficiently. For invoice ingestion, we use an OCR library to extract data from PDFs or connect directly to a dedicated email inbox via IMAP. All data is stored in a PostgreSQL database to create a permanent, auditable record of every action taken on an invoice.
The delivered system is a private API deployed on AWS Lambda, ensuring low operational costs, typically under $50 per month for moderate volumes. The system integrates with your existing accounting software, such as QuickBooks or Xero, to create bills and record payments automatically. You receive the full Python source code, a deployment runbook, and a simple dashboard to monitor invoice status and processing times, which are usually under 5 seconds per invoice.
| Manual AP Workflow | Custom Python AP Workflow |
|---|---|
| Invoice processing time: 15-30 minutes per invoice | Invoice processing time: Under 5 seconds per invoice |
| Approval routing: Manual emails and Slack messages | Approval routing: Automated based on custom rules (amount, vendor, department) |
| Audit trail: Scattered across emails and spreadsheets | Audit trail: Centralized, immutable log in PostgreSQL |
| Error Rate: 5-10% due to manual data entry | Error Rate: Less than 0.1% for data extraction and posting |
What Are the Key Benefits?
One Engineer, Direct Communication
The founder who scopes your project is the engineer who writes the code. There are no project managers or handoffs, which eliminates miscommunication and keeps the project focused.
You Own All the Code
The entire Python codebase is delivered to your private GitHub repository. You get a complete runbook for maintenance and deployment. There is no vendor lock-in.
A 4-Week Build Cycle
A typical accounts payable system with two to three integrations is scoped, built, and deployed in 4 weeks. This timeline includes weekly check-ins and your review.
Predictable Post-Launch Support
After deployment, Syntora offers an optional flat-rate monthly retainer for monitoring, updates, and bug fixes. You get expert support without unpredictable hourly billing.
Deep Financial Systems Experience
Syntora has built financial systems with Plaid for bank syncs, Stripe for payments, and custom PostgreSQL ledgers for automated accounting. This experience is applied directly to your project.
What Does the Process Look Like?
Discovery and Workflow Mapping
In a 45-minute call, we map your current AP process. You receive a detailed scope document within two days outlining the proposed automation, key integrations, and a fixed project price.
Architecture and Integration Plan
You grant read-only access to relevant systems (e.g., accounting software, email inbox). Syntora presents a technical architecture and integration plan for your final approval before the build begins.
Iterative Build and Demo
The system is built over 2-3 weeks with weekly progress demos. You can provide feedback on the approval logic and user notifications to ensure the system fits your team's workflow perfectly.
Deployment and Handoff
The system is deployed to your cloud environment. You receive the full source code, a technical runbook, and user documentation. Syntora provides 4 weeks of post-launch monitoring and support.
Frequently Asked Questions
- What factors determine the cost of a custom AP system?
- The primary factors are the number of vendor invoice formats to support, the complexity of your approval logic, and the number of systems to integrate with. A system that reads PDFs from a single email inbox is simpler than one requiring integrations with multiple vendor portals. You receive a fixed price after the discovery call.
- How long does it take to build and deploy?
- A standard AP automation project takes 4 weeks from kickoff to deployment. This can be faster if you have well-defined approval rules and API access to your existing software. Delays typically arise from waiting for credentials or clarifying ambiguous business logic. The initial discovery session helps create a realistic timeline.
- What happens if something breaks after the project is finished?
- You receive the full source code and a runbook for common maintenance tasks. For ongoing peace of mind, Syntora offers a flat-rate monthly support plan that covers monitoring and bug fixes. You can contact the engineer who built your system directly, ensuring a fast and knowledgeable response.
- Our approval rules are unique. Can a custom system handle them?
- Yes, this is the main reason to build a custom system. Whether it is multi-level approvals based on invoice amount, vendor type, or cross-referencing a budget in a separate spreadsheet, the logic is coded directly into the system. Unlike off-the-shelf tools, there are no limitations on the complexity of your business rules.
- Why not just hire a larger agency or a freelancer?
- Larger agencies add project management overhead, and you rarely speak to the developer. Freelancers may lack experience deploying production-grade financial systems with proper security and logging. Syntora is a single, experienced engineer who handles the entire process, from the first call to final deployment.
- What do we need to provide to get started?
- The main requirements are a point of contact who can clearly explain your current AP process and approval rules. You will also need to provide API keys or credentials for any systems we need to connect to, like your accounting software. Syntora handles all the development, deployment, and infrastructure setup.
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