Cross-border rules can change annually, mid-year or after court and administrative decisions. ExpatEngine therefore treats every high-impact rule as dated data rather than timeless copy.
Source hierarchy
We prefer the responsible tax authority, immigration ministry, justice ministry or EU institution. Legislation and official guidance take priority over accounting-firm articles, blogs and forums.
Verification dates
Important research pages show when the rule set was checked. A future automated workflow can flag pages for review without silently changing tax or immigration logic.
Conflicting or transitional guidance
If official sources appear inconsistent or are explicitly marked as being updated, the site should show uncertainty. Portugal's nationality pages are a current example in this prototype: permanent residence is included, but the citizenship countdown is withheld.
AI use
AI can help draft explanations and code. It is not treated as the authority for thresholds or eligibility. Structured rules must be traceable to sources before they become calculator logic.