Modernizing a Regulated Tax-Compliance Platform for 5,000+ Municipal-Bond Issuers
Legacy Java migrated to .NET Core on private cloud for 5,000+ Obligors—without missing SEC Rule 15c2-12 or IRS filing windows
The Challenge
The client is a leading publisher of continuing-disclosure documents for U.S. municipal bonds. Its Tax Compliance Portal is the system of record for Obligors — cities, counties, school districts, state authorities, and other public entities — managing their bond-proceeds tracking, project expenditures, Private Business Use (PBU) measurements, and statutory record retention under SEC Rule 15c2-12 and IRS tax-exempt-bond regulations.
The legacy portal had been built on older Java technologies and had accumulated years of operational debt: tightly coupled modules, inconsistent code-review practices, accessibility gaps, and increasing difficulty in adapting to evolving regulatory requirements. With more than 5,000 active users depending on the system to remain compliant — and any service degradation directly affecting public-sector issuers’ tax-exempt status — modernization could not be done as a ‘big-bang rewrite.’ The replacement platform had to be delivered incrementally, the calculations had to remain numerically equivalent to the legacy results, and the cutover had to occur outside any active IRS or MSRB filing-deadline windows.
The client also needed the modernized system to be ADA Section 508 compliant and to operate with a substantially stronger application-security and DevSecOps posture than the legacy estate could support.
The Solution
Applied Decision Technologies designed and is delivering an end-to-end remediation: legacy Java APIs replaced by modern .NET Core microservices; a refreshed Angular and HTML5 front-end engineered for ADA Section 508 compliance from the ground up; Microsoft SQL Server Enterprise as the data tier; private-cloud hosting with TLS 1.2+ in transit and AES-256 encryption at rest; and a JWT-based authentication model with token refresh and state-token request/response binding.
Functionally, the modernized platform tracks bond proceeds and project expenditures with audit-grade detail; runs PBU measurements against IRS thresholds with documented numerical-precision policy; manages comprehensive record retention under configurable retention schedules; provides custom dashboards and configurable reports for Obligor finance and compliance staff; and surfaces compliance alerts when project usage trends towards regulatory thresholds.
Cutover was executed via feature-flagged, per-Obligor rollout — converting a single high-risk migration into a sequence of small, reversible deployments. Each per-Obligor cutover was followed by a 60-day continuous-reconciliation window in which legacy and modern calculations were compared at full record fidelity. The legacy engine was retained in shadow mode for an additional reconciliation period after each final cutover, providing a fall-back recalculation path if any discrepancy surfaced. Final cutovers were deliberately scheduled outside active IRS and MSRB filing-deadline windows.
Outcomes
The modernized platform supports 5,000+ active Obligor users today on .NET Core microservices, with custom reports, role-based access controls aligned to Obligor staffing structures, and an ADA Section 508-compliant front-end that has stood up to accessibility review.
Total cumulative user-visible downtime across the per-Obligor cutover sequence was measured in minutes rather than hours — limited to brief scheduled maintenance windows during flag flips. No Obligor missed an IRS or MSRB filing deadline as a consequence of the migration. PBU and bond-proceeds calculations reconcile cleanly against legacy results within the documented precision tolerance.
The engineering disciplines institutionalized on this engagement — codified numerical-precision policy, reusable reconciliation harness, feature-flagged per-tenant rollouts, deliberate cutover-window scheduling, shadow-mode legacy retention — have since become standard ADecTec migration patterns and are directly transferable to other regulated workloads.
Why It Matters
Migrating a regulated, multi-thousand-user financial system without service disruption is a discipline more than a technology choice. ADecTec demonstrated that discipline on this engagement: not by avoiding the hard problems but by engineering cleanly through them.
For any organization operating a legacy financial, healthcare, or regulatory system that needs modernization without business interruption — and where calculation accuracy is regulatory-impact-grade — ADecTec brings a proven, tested playbook.