Initial extraction from monorepo

fire_planner/tax/nomad.py

@@ -0,0 +1,31 @@
+"""Perpetual-traveller / nomad regime — 0% income tax + 1% regulatory
+risk premium on all flows.
+
+The 1% premium captures the real-world risk that a "no tax residence"
+posture eventually attracts adverse rulings, the OECD CRS net tightens,
+or a destination starts taxing previously-exempt foreign income (e.g.
+Thailand 2024 remittance rule). We don't try to model the actual
+mechanism — it's a Bayesian fudge factor. Tunable via the constructor.
+"""
+from __future__ import annotations
+
+from decimal import Decimal
+
+from fire_planner.tax.base import TaxBreakdown, TaxInputs, TaxRegime
+
+
+class NomadTaxRegime(TaxRegime):
+    name = "nomad"
+
+    def __init__(self, regulatory_premium_rate: Decimal = Decimal("0.01")) -> None:
+        self.regulatory_premium_rate = regulatory_premium_rate
+
+    def compute_tax(self, inputs: TaxInputs) -> TaxBreakdown:
+        # ISA withdrawals are tax-free in the UK; for a nomad they're
+        # just cash. The risk premium applies to cash that flows
+        # *outside* a UK wrapper because that's the boundary the
+        # premium is hedging.
+        chargeable = (inputs.earned_income + inputs.pension_withdrawal + inputs.capital_gains +
+                      inputs.dividends + inputs.interest)
+        return TaxBreakdown(other=chargeable * self.regulatory_premium_rate,
+                            notes=("nomad", f"premium_rate={self.regulatory_premium_rate}"))