Building a Residency Logic Engine

Residency determination looks simple. Until you're the one building logic around multiple jurisdictions, partial years, tie-breakers, and travel logs.

In Residex, we started by mapping the most common rules: 183-day thresholds, permanent home, habitual abode. But what mattered most was interpretability — making the logic traceable, auditable, and adjustable.

We designed the core engine around modular conditions. Each rule runs independently, returns a reason, and passes its result up to a resolver. That lets users see not just what the system says, but why.

The goal? Replace time-consuming advisory work with clean, trustworthy software logic.