Bespoke Financial Workflow Automation Suite

Problem

Supplier payments, subcontractor payment certificates and CIS payment sheets were produced through manual steps and manual approval chains. Each document had to be assembled by hand, passed between people for sign-off, and reconciled before payment, and the process depended on a dedicated administrative role to keep it moving. There was no single structured record of what had been requested, approved and paid.

Constraints

Subcontractor payments carry CIS, HMRC and BACS requirements, so the calculations and outputs had to be correct and traceable rather than approximately right. Approvals needed multiple authorisation levels and a signature that could be captured digitally instead of on paper. The solution also had to be owned end to end: designed around the business's own process, not bent to fit a generic tool's data model, and structured so new payment types could be added later without a redesign.

Approach

I engineered the suite as a standalone, custom-built system rather than a configuration of an existing product. The starting point was the schema: a tailored data model designed for operational efficiency, with separate, well-defined entities for requests, approvals, certificates and payment outputs. On top of it I built a bespoke workflow engine that moves each record through defined stages (submission, multi-level authorisation, e-signature, payment output) and a logic layer that applies the CIS, HMRC and BACS rules inside the system, so the correct figures and file outputs are produced by the process itself instead of being assembled by hand.

Outcome

The suite eliminated a full administrative role and replaced manual approval chains with structured digital workflows, including e-signature and multi-level authorisation. Every payment request, certificate and payment sheet now lives in a structured record with a clear approval history, in place of documents passed between people.

What I'd do differently

The natural next step is to extend the same framework to further payment and approval workflows as new modules, reusing the existing schema, logic layer and approval pipeline rather than starting each one from scratch.

Architecture

The suite is easiest to understand as two flows: a payment calculation flow that produces a payable amount, and an approval workflow that routes the resulting certificate.

Subcontractor payment calculation flow

The calculation branches on whether a payment is due. When it is, the system applies the selected retention option, stores the accumulated retention against the subcontractor record, then applies the VAT treatment (standard, zero-rated or reverse charge) and the CIS deduction to arrive at the payable amount. When nothing is due, the same tax branches run against the accumulated retention being released. The payable amount becomes a payment certificate, which only reaches the final approver once both approvers have approved.

Approval workflow with configurable bypass

Each certificate is submitted with a bypass option that decides which approval stages apply. Whichever route is chosen, the record always ends at the final approver, and each stage sends its own email notification.

The design decision that mattered most was building the schema and logic layer as the foundation and treating each payment workflow as a module on top of it. Supplier payments, subcontractor certificates and CIS payment sheets differ in their rules but share the same approval and documentation pattern, so a new workflow means adding a module, not redesigning the system.