diff --git a/revenue-tax-exemption-controls/README.md b/revenue-tax-exemption-controls/README.md
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+# Revenue Tax Exemption Controls
+
+This module adds a focused Revenue Infrastructure slice for institutional tax exemption and grant billing compliance. It avoids live payment credentials and evaluates invoice readiness with deterministic local data.
+
+## What it checks
+
+- Expired or missing exemption certificates
+- Reverse-charge invoices without VAT ID evidence
+- Tax amount mismatch against configured jurisdictions
+- Unknown tax jurisdictions that require finance review
+- Grant budget overrun risk
+- Invoice line categories outside grant-approved spend
+- Payment settlement events that are missing or mismatched
+- Invoice-level recommended actions and an audit digest
+
+## Run locally
+
+```bash
+npm run check
+npm test
+npm run demo
+```
+
+The sample data intentionally places two invoices on hold: one has an expired exemption certificate, grant-category drift, and settlement mismatch; the other has missing VAT ID evidence for reverse charge.
diff --git a/revenue-tax-exemption-controls/demo.js b/revenue-tax-exemption-controls/demo.js
new file mode 100644
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+++ b/revenue-tax-exemption-controls/demo.js
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+"use strict";
+
+const sampleBundle = require("./sample-data.json");
+const {
+  analyzeRevenueTaxControls,
+} = require("./src/revenue-tax-exemption-controls");
+
+const result = analyzeRevenueTaxControls(sampleBundle);
+
+console.log(`Decision: ${result.decision}`);
+console.log(`Audit digest: ${result.auditDigest}`);
+console.log("");
+console.log("Invoice summaries:");
+for (const summary of result.invoiceSummaries) {
+  console.log(`- ${summary.invoiceId}: ${summary.recommendedAction} (${summary.blockerCount} blocker, ${summary.warningCount} warning)`);
+}
+console.log("");
+console.log("Findings:");
+for (const finding of result.findings) {
+  console.log(`- [${finding.severity}] ${finding.invoiceId} ${finding.id}: ${finding.title}`);
+  console.log(`  detail: ${finding.detail}`);
+  console.log(`  remediation: ${finding.remediation}`);
+}
diff --git a/revenue-tax-exemption-controls/docs/requirement-map.md b/revenue-tax-exemption-controls/docs/requirement-map.md
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+# Requirement Map
+
+| Revenue Infrastructure requirement | Implementation |
+| --- | --- |
+| Institutional billing | Customers include institutional tax profiles, jurisdictions, exemption certificates, and VAT/reverse-charge evidence. |
+| Invoice controls | Invoices include subscription/compute line items, tax jurisdictions, tax cents, grant budget IDs, and gross amount summaries. |
+| Grants and cost controls | Grant budgets enforce approved spend totals and allowed line-item categories. |
+| Payment/settlement evidence | Settlement events are reconciled against invoice gross amounts before revenue can be treated as cleanly billable. |
+| Compliance holds | Blockers produce `billing-hold`; warnings produce `finance-review`; clean invoices produce `billable`. |
+| Auditability | Results include invoice summaries, findings, recommended actions, and a deterministic `sha256` audit digest. |
+
+## Demo Video
+
+The PR includes `docs/tax-exemption-demo.mp4`, a real terminal walkthrough running the local check, test, and demo scripts.
diff --git a/revenue-tax-exemption-controls/docs/tax-exemption-demo.mp4 b/revenue-tax-exemption-controls/docs/tax-exemption-demo.mp4
new file mode 100644
index 0000000..0803a84
Binary files /dev/null and b/revenue-tax-exemption-controls/docs/tax-exemption-demo.mp4 differ
diff --git a/revenue-tax-exemption-controls/package.json b/revenue-tax-exemption-controls/package.json
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--- /dev/null
+++ b/revenue-tax-exemption-controls/package.json
@@ -0,0 +1,12 @@
+{
+  "name": "revenue-tax-exemption-controls",
+  "version": "1.0.0",
+  "description": "Institutional tax exemption and grant billing compliance controls.",
+  "main": "src/revenue-tax-exemption-controls.js",
+  "scripts": {
+    "check": "node --check src/revenue-tax-exemption-controls.js && node --check test.js && node --check demo.js",
+    "test": "node test.js",
+    "demo": "node demo.js"
+  },
+  "license": "MIT"
+}
diff --git a/revenue-tax-exemption-controls/sample-data.json b/revenue-tax-exemption-controls/sample-data.json
new file mode 100644
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--- /dev/null
+++ b/revenue-tax-exemption-controls/sample-data.json
@@ -0,0 +1,97 @@
+{
+  "now": "2026-05-15T00:00:00.000Z",
+  "customers": [
+    {
+      "id": "cust-university-lab",
+      "name": "Northbridge University Lab",
+      "taxProfile": {
+        "jurisdiction": "US-CA",
+        "exemptionStatus": "exempt",
+        "reverseCharge": false,
+        "vatId": null,
+        "exemptionCertificate": {
+          "id": "cert-2025-ca-221",
+          "status": "verified",
+          "expiresAt": "2026-04-01T00:00:00.000Z"
+        }
+      }
+    },
+    {
+      "id": "cust-eu-institute",
+      "name": "Helix EU Institute",
+      "taxProfile": {
+        "jurisdiction": "DE",
+        "exemptionStatus": "standard",
+        "reverseCharge": true,
+        "vatId": "",
+        "exemptionCertificate": null
+      }
+    }
+  ],
+  "grantBudgets": [
+    {
+      "id": "grant-nih-atlas-2026",
+      "approvedCents": 300000,
+      "usedCents": 252000,
+      "allowedCategories": ["subscription", "storage"]
+    },
+    {
+      "id": "grant-eu-knowledge-graph",
+      "approvedCents": 220000,
+      "usedCents": 80000,
+      "allowedCategories": ["subscription", "compute", "storage"]
+    }
+  ],
+  "invoices": [
+    {
+      "id": "inv-1007",
+      "customerId": "cust-university-lab",
+      "taxJurisdiction": "US-CA",
+      "grantBudgetId": "grant-nih-atlas-2026",
+      "taxCents": 0,
+      "lines": [
+        {
+          "description": "SCIBASE Enterprise workspace",
+          "category": "subscription",
+          "quantity": 1,
+          "unitCents": 42000
+        },
+        {
+          "description": "GPU compute overage",
+          "category": "compute",
+          "quantity": 1,
+          "unitCents": 12000
+        }
+      ]
+    },
+    {
+      "id": "inv-1008",
+      "customerId": "cust-eu-institute",
+      "taxJurisdiction": "DE",
+      "grantBudgetId": "grant-eu-knowledge-graph",
+      "taxCents": 0,
+      "lines": [
+        {
+          "description": "Knowledge graph API seats",
+          "category": "subscription",
+          "quantity": 2,
+          "unitCents": 18000
+        }
+      ]
+    }
+  ],
+  "settlementEvents": [
+    {
+      "invoiceId": "inv-1007",
+      "status": "settled",
+      "amountCents": 51000,
+      "processor": "stripe"
+    },
+    {
+      "invoiceId": "inv-1008",
+      "status": "settled",
+      "amountCents": 36000,
+      "processor": "stripe"
+    }
+  ]
+}
diff --git a/revenue-tax-exemption-controls/src/revenue-tax-exemption-controls.js b/revenue-tax-exemption-controls/src/revenue-tax-exemption-controls.js
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--- /dev/null
+++ b/revenue-tax-exemption-controls/src/revenue-tax-exemption-controls.js
@@ -0,0 +1,260 @@
+"use strict";
+
+const crypto = require("node:crypto");
+
+const TAX_RATES = {
+  "US-CA": 0.0875,
+  "US-MA": 0.0625,
+  "GB": 0.2,
+  "DE": 0.19,
+};
+
+function stableStringify(value) {
+  if (Array.isArray(value)) return `[${value.map(stableStringify).join(",")}]`;
+  if (value && typeof value === "object") {
+    return `{${Object.keys(value)
+      .sort()
+      .map((key) => `${JSON.stringify(key)}:${stableStringify(value[key])}`)
+      .join(",")}}`;
+  }
+  return JSON.stringify(value);
+}
+
+function stableHash(value) {
+  return crypto.createHash("sha256").update(stableStringify(value)).digest("hex");
+}
+
+function requireFields(object, fields, label) {
+  const missing = fields.filter((field) => object[field] === undefined || object[field] === null);
+  if (missing.length > 0) throw new Error(`${label} is missing required field(s): ${missing.join(", ")}`);
+}
+
+function parseDate(value) {
+  const parsed = new Date(value);
+  if (Number.isNaN(parsed.getTime())) throw new Error(`Invalid date: ${value}`);
+  return parsed;
+}
+
+function finding(severity, id, invoiceId, title, detail, remediation) {
+  return { severity, id, invoiceId, title, detail, remediation };
+}
+
+function centsForLines(lines) {
+  return lines.reduce((total, line) => total + line.quantity * line.unitCents, 0);
+}
+
+function expectedTaxCents(invoice, customer) {
+  if (customer.taxProfile.exemptionStatus === "exempt") return 0;
+  if (customer.taxProfile.reverseCharge === true) return 0;
+  const rate = TAX_RATES[invoice.taxJurisdiction];
+  if (rate === undefined) return null;
+  return Math.round(centsForLines(invoice.lines) * rate);
+}
+
+function hasCurrentExemption(customer, now) {
+  const certificate = customer.taxProfile.exemptionCertificate;
+  if (!certificate) return false;
+  return certificate.status === "verified" && parseDate(certificate.expiresAt) > now;
+}
+
+function evaluateTaxTreatment(invoice, customer, now) {
+  const findings = [];
+  const expectedTax = expectedTaxCents(invoice, customer);
+
+  if (customer.taxProfile.exemptionStatus === "exempt" && !hasCurrentExemption(customer, now)) {
+    findings.push(finding(
+      "blocker",
+      "exemption-certificate-expired",
+      invoice.id,
+      "Invoice claims tax exemption without current certificate",
+      `${customer.name} is marked exempt but the exemption certificate is missing, unverified, or expired.`,
+      "Put the invoice on billing hold until a current exemption certificate is verified.",
+    ));
+  }
+
+  if (customer.taxProfile.reverseCharge === true && !customer.taxProfile.vatId) {
+    findings.push(finding(
+      "blocker",
+      "reverse-charge-vat-id-missing",
+      invoice.id,
+      "Reverse charge invoice lacks VAT ID evidence",
+      `${customer.name} uses reverse charge but has no VAT ID on file.`,
+      "Collect and verify the VAT ID before issuing the invoice with zero tax.",
+    ));
+  }
+
+  if (expectedTax === null) {
+    findings.push(finding(
+      "warning",
+      "unknown-tax-jurisdiction",
+      invoice.id,
+      "Tax jurisdiction has no configured rate",
+      `${invoice.taxJurisdiction} is not present in the configured tax rate table.`,
+      "Route the invoice to finance review before issuance.",
+    ));
+  } else if (invoice.taxCents !== expectedTax) {
+    findings.push(finding(
+      "blocker",
+      "tax-amount-mismatch",
+      invoice.id,
+      "Invoice tax does not match configured treatment",
+      `Expected ${expectedTax} cents but invoice records ${invoice.taxCents} cents.`,
+      "Recalculate tax or correct exemption/reverse-charge evidence before billing.",
+    ));
+  }
+
+  return findings;
+}
+
+function evaluateGrantControls(invoice, grantBudgets) {
+  const findings = [];
+  const grant = grantBudgets.find((budget) => budget.id === invoice.grantBudgetId);
+
+  if (!grant) {
+    findings.push(finding(
+      "warning",
+      "grant-budget-missing",
+      invoice.id,
+      "Invoice is not attached to a grant budget",
+      `${invoice.id} has no recognized grant budget.`,
+      "Attach a grant or mark the invoice as non-grant commercial revenue.",
+    ));
+    return findings;
+  }
+
+  const usedCents = grant.usedCents + centsForLines(invoice.lines);
+  if (usedCents > grant.approvedCents) {
+    findings.push(finding(
+      "blocker",
+      "grant-budget-exceeded",
+      invoice.id,
+      "Invoice would exceed approved grant budget",
+      `${grant.id} would exceed its approved amount by ${usedCents - grant.approvedCents} cents.`,
+      "Hold billing until the grant budget is expanded or line items are moved to another funding source.",
+    ));
+  }
+
+  for (const line of invoice.lines) {
+    if (!grant.allowedCategories.includes(line.category)) {
+      findings.push(finding(
+        "blocker",
+        "grant-category-disallowed",
+        invoice.id,
+        "Invoice line item is outside grant-approved categories",
+        `${line.description} uses category ${line.category}, which is not allowed by ${grant.id}.`,
+        "Remove the line item from the grant invoice or obtain written budget approval.",
+      ));
+    }
+  }
+
+  return findings;
+}
+
+function evaluateSettlement(invoice, settlementEvents) {
+  const findings = [];
+  const settled = settlementEvents.find((event) => event.invoiceId === invoice.id && event.status === "settled");
+  const grossCents = centsForLines(invoice.lines) + invoice.taxCents;
+
+  if (!settled) {
+    findings.push(finding(
+      "warning",
+      "settlement-event-missing",
+      invoice.id,
+      "Invoice has no settled payment event",
+      `${invoice.id} has no processor settlement event yet.`,
+      "Keep fulfillment entitlements provisional until settlement is recorded.",
+    ));
+    return findings;
+  }
+
+  if (settled.amountCents !== grossCents) {
+    findings.push(finding(
+      "blocker",
+      "settlement-amount-mismatch",
+      invoice.id,
+      "Payment settlement does not match invoice gross amount",
+      `Expected settlement ${grossCents} cents but received ${settled.amountCents} cents.`,
+      "Reconcile processor fees, credits, refunds, or invoice amount before recognizing payment.",
+    ));
+  }
+
+  return findings;
+}
+
+function buildInvoiceSummary(invoice, findings) {
+  const invoiceFindings = findings.filter((item) => item.invoiceId === invoice.id);
+  const blockerCount = invoiceFindings.filter((item) => item.severity === "blocker").length;
+  const warningCount = invoiceFindings.filter((item) => item.severity === "warning").length;
+  let recommendedAction = "issue-invoice";
+  if (blockerCount > 0) recommendedAction = "billing-hold";
+  else if (warningCount > 0) recommendedAction = "finance-review";
+
+  return {
+    invoiceId: invoice.id,
+    grossCents: centsForLines(invoice.lines) + invoice.taxCents,
+    taxCents: invoice.taxCents,
+    blockerCount,
+    warningCount,
+    recommendedAction,
+  };
+}
+
+function decide(findings) {
+  if (findings.some((item) => item.severity === "blocker")) return "billing-hold";
+  if (findings.some((item) => item.severity === "warning")) return "finance-review";
+  return "billable";
+}
+
+function assertBundle(bundle) {
+  requireFields(bundle, ["customers", "invoices", "grantBudgets", "settlementEvents"], "revenue controls bundle");
+}
+
+function analyzeRevenueTaxControls(bundle, options = {}) {
+  assertBundle(bundle);
+  const now = parseDate(options.now || bundle.now || new Date().toISOString());
+  const findings = [];
+
+  for (const invoice of bundle.invoices) {
+    requireFields(invoice, ["id", "customerId", "taxJurisdiction", "taxCents", "lines"], `invoice ${invoice.id || "(unknown)"}`);
+    const customer = bundle.customers.find((item) => item.id === invoice.customerId);
+    if (!customer) {
+      findings.push(finding(
+        "blocker",
+        "invoice-customer-missing",
+        invoice.id,
+        "Invoice customer is missing",
+        `${invoice.id} references unknown customer ${invoice.customerId}.`,
+        "Attach a valid customer record before billing.",
+      ));
+      continue;
+    }
+    requireFields(customer, ["id", "name", "taxProfile"], `customer ${customer.id}`);
+    findings.push(...evaluateTaxTreatment(invoice, customer, now));
+    findings.push(...evaluateGrantControls(invoice, bundle.grantBudgets));
+    findings.push(...evaluateSettlement(invoice, bundle.settlementEvents));
+  }
+
+  const invoiceSummaries = bundle.invoices.map((invoice) => buildInvoiceSummary(invoice, findings));
+  const decision = decide(findings);
+  const auditDigest = stableHash({
+    decision,
+    invoiceSummaries,
+    findings,
+    evaluatedAt: now.toISOString(),
+  });
+
+  return {
+    evaluatedAt: now.toISOString(),
+    decision,
+    findings,
+    invoiceSummaries,
+    auditDigest: `sha256:${auditDigest}`,
+  };
+}
+
+module.exports = {
+  TAX_RATES,
+  analyzeRevenueTaxControls,
+  stableHash,
+  stableStringify,
+};
diff --git a/revenue-tax-exemption-controls/test.js b/revenue-tax-exemption-controls/test.js
new file mode 100644
index 0000000..64d7668
--- /dev/null
+++ b/revenue-tax-exemption-controls/test.js
@@ -0,0 +1,44 @@
+"use strict";
+
+const assert = require("node:assert/strict");
+const sampleBundle = require("./sample-data.json");
+const {
+  analyzeRevenueTaxControls,
+  stableHash,
+} = require("./src/revenue-tax-exemption-controls");
+
+function clone(value) {
+  return JSON.parse(JSON.stringify(value));
+}
+
+function ids(result) {
+  return new Set(result.findings.map((finding) => finding.id));
+}
+
+const held = analyzeRevenueTaxControls(sampleBundle);
+const heldIds = ids(held);
+
+assert.equal(held.decision, "billing-hold");
+assert.match(held.auditDigest, /^sha256:[a-f0-9]{64}$/);
+assert(heldIds.has("exemption-certificate-expired"));
+assert(heldIds.has("grant-budget-exceeded"));
+assert(heldIds.has("grant-category-disallowed"));
+assert(heldIds.has("settlement-amount-mismatch"));
+assert(heldIds.has("reverse-charge-vat-id-missing"));
+assert.equal(held.invoiceSummaries.find((item) => item.invoiceId === "inv-1007").recommendedAction, "billing-hold");
+
+const billableBundle = clone(sampleBundle);
+billableBundle.customers[0].taxProfile.exemptionCertificate.expiresAt = "2026-12-31T00:00:00.000Z";
+billableBundle.customers[1].taxProfile.vatId = "DE123456789";
+billableBundle.grantBudgets[0].approvedCents = 330000;
+billableBundle.grantBudgets[0].allowedCategories.push("compute");
+billableBundle.settlementEvents[0].amountCents = 54000;
+
+const billable = analyzeRevenueTaxControls(billableBundle);
+assert.equal(billable.decision, "billable");
+assert.equal(billable.findings.length, 0);
+assert.equal(billable.invoiceSummaries.every((item) => item.recommendedAction === "issue-invoice"), true);
+assert.notEqual(held.auditDigest, billable.auditDigest);
+assert.equal(stableHash({ b: 2, a: 1 }), stableHash({ a: 1, b: 2 }));
+
+console.log("revenue tax exemption control tests passed");