diff --git a/.vite/fixtures/cdp-uploader.js b/.vite/fixtures/cdp-uploader.js
index cec1c2e1..49699f05 100644
--- a/.vite/fixtures/cdp-uploader.js
+++ b/.vite/fixtures/cdp-uploader.js
@@ -61,7 +61,7 @@ const callbackReceiverFixture = {
 const cdpUploaderStackFixture = {
   // Depends on callbackReceiver to ensure correct initialisation order
   cdpUploaderStack: [
-    async ({ callbackReceiver }, use) => {
+    async ({ callbackReceiver: _ }, use) => {
       // Disable vitest-fetch-mock so we can make real HTTP requests to containers
       // The global fetch is mocked by default in .vite/setup-files.js
       if (globalThis.fetchMock) {
diff --git a/.vite/fixtures/server-with-db.js b/.vite/fixtures/server-with-db.js
index 0909a68c..2286c630 100644
--- a/.vite/fixtures/server-with-db.js
+++ b/.vite/fixtures/server-with-db.js
@@ -4,7 +4,6 @@ export const it = dbTest.extend({
   server: [
     async ({ db }, use) => {
       // db parameter triggers MongoDB setup (unused directly)
-      // eslint-disable-next-line no-unused-vars
       const _dbUri = db
       const { createServer } = await import('#server/server.js')
       const server = await createServer()
diff --git a/eslint.config.js b/eslint.config.js
index efaae014..4f836159 100644
--- a/eslint.config.js
+++ b/eslint.config.js
@@ -24,5 +24,17 @@ export default [
     rules: {
       'n/no-unpublished-import': 'off'
     }
+  },
+  {
+    rules: {
+      'no-unused-vars': [
+        'error',
+        {
+          argsIgnorePattern: '^_',
+          caughtErrorsIgnorePattern: '^_',
+          varsIgnorePattern: '^_'
+        }
+      ]
+    }
   }
 ]
diff --git a/scripts/mongo-performance-test/separate-collections/create-collections.js b/scripts/mongo-performance-test/separate-collections/create-collections.js
index b593985b..104d4e94 100644
--- a/scripts/mongo-performance-test/separate-collections/create-collections.js
+++ b/scripts/mongo-performance-test/separate-collections/create-collections.js
@@ -14,7 +14,7 @@ export async function createOrganisationCollection(
     try {
       await db.collection(collectionName).drop()
       console.log('Dropped existing organisation collection')
-    } catch (error) {
+    } catch (_error) {
       console.log('Organisation collection does not exist, creating new')
     }
 
@@ -149,7 +149,7 @@ export async function createRegistrationCollection(
     try {
       await db.collection(collectionName).drop()
       console.log('Dropped existing registration collection')
-    } catch (error) {
+    } catch (_error) {
       console.log('Registration collection does not exist, creating new')
     }
 
@@ -355,7 +355,7 @@ export async function createAccreditationCollection(
     try {
       await db.collection(collectionName).drop()
       console.log('Dropped existing accreditation collection')
-    } catch (error) {
+    } catch (_error) {
       console.log('Accreditation collection does not exist, creating new')
     }
 
diff --git a/scripts/mongo-performance-test/single-nested-collection/create-collection.js b/scripts/mongo-performance-test/single-nested-collection/create-collection.js
index f7d76d68..cdb0efaa 100644
--- a/scripts/mongo-performance-test/single-nested-collection/create-collection.js
+++ b/scripts/mongo-performance-test/single-nested-collection/create-collection.js
@@ -15,7 +15,7 @@ export async function createOrganisationCollection(
     try {
       await db.collection(collectionName).drop()
       console.log('Dropped existing collection')
-    } catch (error) {
+    } catch (_error) {
       console.log('Collection does not exist, creating new')
     }
 
diff --git a/sonar-project.properties b/sonar-project.properties
index 068bcb34..f940bba1 100644
--- a/sonar-project.properties
+++ b/sonar-project.properties
@@ -19,3 +19,8 @@ sonar.test.inclusions=src/**/*.test.js,src/**/*.contract.js
 
 sonar.javascript.lcov.reportPaths=./coverage/lcov.info
 sonar.coverage.exclusions=src/index.js,src/common/helpers/secure-context.js,src/domain/organisations/model.js
+
+# Disable S1481 - we use _ prefix for intentionally unused variables (enforced by ESLint)
+sonar.issue.ignore.multicriteria=e1
+sonar.issue.ignore.multicriteria.e1.ruleKey=javascript:S1481
+sonar.issue.ignore.multicriteria.e1.resourceKey=**/*
diff --git a/src/common/helpers/collections/create-update.seed-data.test.js b/src/common/helpers/collections/create-update.seed-data.test.js
index 22c6eaf3..32e1a294 100644
--- a/src/common/helpers/collections/create-update.seed-data.test.js
+++ b/src/common/helpers/collections/create-update.seed-data.test.js
@@ -38,7 +38,7 @@ describe('createSeedData', () => {
     }
   )
 
-  it('creates seed data when there are no documents already in epr-organisations collection', async (collectionName) => {
+  it('creates seed data when there are no documents already in epr-organisations collection', async () => {
     const { mockDb } = createMockDb({
       countDocuments: async () => 0
     })
diff --git a/src/common/helpers/s3/s3-client.test.js b/src/common/helpers/s3/s3-client.test.js
index 73151112..e5c28403 100644
--- a/src/common/helpers/s3/s3-client.test.js
+++ b/src/common/helpers/s3/s3-client.test.js
@@ -14,7 +14,7 @@ describe('createS3Client', () => {
   beforeEach(() => {
     s3Client = { config: { region } }
 
-    vi.mocked(S3Client).mockImplementation(function (config) {
+    vi.mocked(S3Client).mockImplementation(function () {
       return s3Client
     })
   })
diff --git a/src/forms-submission-data/migrate-forms-data.test.js b/src/forms-submission-data/migrate-forms-data.test.js
index a36901ac..e5a97bdd 100644
--- a/src/forms-submission-data/migrate-forms-data.test.js
+++ b/src/forms-submission-data/migrate-forms-data.test.js
@@ -1,17 +1,17 @@
-import { beforeEach, describe, expect, it, vi } from 'vitest'
-import { migrateFormsData } from './migrate-forms-data.js'
-import { logger } from '#common/helpers/logging/logger.js'
-import { createFormSubmissionsRepository } from '#repositories/form-submissions/inmemory.js'
-import { createInMemoryOrganisationsRepository } from '#repositories/organisations/inmemory.js'
-import { readdirSync, readFileSync } from 'fs'
-import { join } from 'path'
 import {
   LOGGING_EVENT_ACTIONS,
   LOGGING_EVENT_CATEGORIES
 } from '#common/enums/index.js'
-import { MATERIAL } from '#domain/organisations/model.js'
-import reprocessorGlassAccreditation from '#data/fixtures/ea/accreditation/reprocessor-glass.json'
+import { logger } from '#common/helpers/logging/logger.js'
 import exporterAccreditation from '#data/fixtures/ea/accreditation/exporter.json'
+import reprocessorGlassAccreditation from '#data/fixtures/ea/accreditation/reprocessor-glass.json'
+import { MATERIAL } from '#domain/organisations/model.js'
+import { createFormSubmissionsRepository } from '#repositories/form-submissions/inmemory.js'
+import { createInMemoryOrganisationsRepository } from '#repositories/organisations/inmemory.js'
+import { readdirSync, readFileSync } from 'fs'
+import { join } from 'path'
+import { beforeEach, describe, expect, it, vi } from 'vitest'
+import { migrateFormsData } from './migrate-forms-data.js'
 
 vi.mock('#common/helpers/logging/logger.js', () => ({
   logger: {
diff --git a/src/repositories/organisations/contract/insert.contract.js b/src/repositories/organisations/contract/insert.contract.js
index e7d59b71..6d66435f 100644
--- a/src/repositories/organisations/contract/insert.contract.js
+++ b/src/repositories/organisations/contract/insert.contract.js
@@ -1,4 +1,4 @@
-import { describe, beforeEach, expect } from 'vitest'
+import { beforeEach, describe, expect } from 'vitest'
 import { buildOrganisation } from './test-data.js'
 
 export const testInsertBehaviour = (it) => {
@@ -24,14 +24,14 @@ export const testInsertBehaviour = (it) => {
           ...orgWithoutStatusHistory,
           formSubmissionTime: new Date(orgData.formSubmissionTime),
           registrations: orgData.registrations.map((reg) => {
-            const { statusHistory, ...regWithoutStatusHistory } = reg
+            const { statusHistory: _, ...regWithoutStatusHistory } = reg
             return {
               ...regWithoutStatusHistory,
               formSubmissionTime: new Date(reg.formSubmissionTime)
             }
           }),
           accreditations: orgData.accreditations.map((acc) => {
-            const { statusHistory, ...accWithoutStatusHistory } = acc
+            const { statusHistory: _, ...accWithoutStatusHistory } = acc
             return {
               ...accWithoutStatusHistory,
               formSubmissionTime: new Date(acc.formSubmissionTime)
diff --git a/src/repositories/organisations/contract/update.contract.js b/src/repositories/organisations/contract/update.contract.js
index d8c584d7..4cf430df 100644
--- a/src/repositories/organisations/contract/update.contract.js
+++ b/src/repositories/organisations/contract/update.contract.js
@@ -146,7 +146,7 @@ export const testUpdateBehaviour = (it) => {
         )
         expect(addedReg).toBeDefined()
 
-        const { statusHistory, ...expectedReg } = {
+        const { statusHistory: _, ...expectedReg } = {
           ...newRegistration,
           formSubmissionTime: new Date(newRegistration.formSubmissionTime)
         }
@@ -184,7 +184,7 @@ export const testUpdateBehaviour = (it) => {
         )
         expect(addedAcc).toBeDefined()
 
-        const { statusHistory, ...expectedAcc } = {
+        const { statusHistory: _, ...expectedAcc } = {
           ...newAccreditation,
           formSubmissionTime: new Date(newAccreditation.formSubmissionTime)
         }
diff --git a/src/repositories/organisations/helpers.js b/src/repositories/organisations/helpers.js
index 7b6777f0..c77e376e 100644
--- a/src/repositories/organisations/helpers.js
+++ b/src/repositories/organisations/helpers.js
@@ -61,7 +61,7 @@ export const mergeItemsWithUpdates = (existingItems, itemUpdates) => {
   }))
 
   return [...processedExisting, ...newItems].map((item) => {
-    const { status, ...remainingFields } = item
+    const { status: _, ...remainingFields } = item
     return remainingFields
   })
 }
@@ -93,7 +93,7 @@ const normalizeItem = (item) => {
   if (!item) {
     return item
   }
-  const { status, statusHistory, ...rest } = item
+  const { status: _, statusHistory: _s, ...rest } = item
   return rest
 }
 
@@ -102,7 +102,14 @@ export const normalizeForComparison = (org) => {
     return org
   }
 
-  const { version, schemaVersion, status, statusHistory, users, ...rest } = org
+  const {
+    schemaVersion: _sv,
+    status: _s,
+    statusHistory: _sh,
+    users: _u,
+    version: _v,
+    ...rest
+  } = org
 
   const normalized = {
     ...rest,
diff --git a/src/repositories/organisations/inmemory.js b/src/repositories/organisations/inmemory.js
index 10925cb7..0fb27f5f 100644
--- a/src/repositories/organisations/inmemory.js
+++ b/src/repositories/organisations/inmemory.js
@@ -1,18 +1,18 @@
-import {
-  validateId,
-  validateOrganisationInsert,
-  validateOrganisationUpdate
-} from './schema/index.js'
+import Boom from '@hapi/boom'
 import {
   SCHEMA_VERSION,
   collateUsersOnApproval,
   createInitialStatusHistory,
   getCurrentStatus,
-  statusHistoryWithChanges,
+  hasChanges,
   mergeSubcollection,
-  hasChanges
+  statusHistoryWithChanges
 } from './helpers.js'
-import Boom from '@hapi/boom'
+import {
+  validateId,
+  validateOrganisationInsert,
+  validateOrganisationUpdate
+} from './schema/index.js'
 
 // Aggressive retry settings for in-memory testing (setImmediate() is microseconds)
 const MAX_CONSISTENCY_RETRIES = 5
@@ -104,7 +104,7 @@ const performUpdate =
       )
     }
 
-    const { status, ...merged } = { ...existing, ...validatedUpdates }
+    const { status: _, ...merged } = { ...existing, ...validatedUpdates }
 
     const registrations = mergeSubcollection(
       existing.registrations,
@@ -146,7 +146,7 @@ const performUpsert =
   (storage, staleCache, pendingSyncRef, insertFn, updateFn) =>
   async (organisation) => {
     const validated = validateOrganisationInsert(organisation)
-    const { id, version, schemaVersion, ...updateData } = validated
+    const { id, version: _v, schemaVersion: _s, ...updateData } = validated
 
     const existing = storage.find((o) => o.id === id)
 
diff --git a/src/repositories/organisations/mongodb.js b/src/repositories/organisations/mongodb.js
index a60e1dc3..b027151c 100644
--- a/src/repositories/organisations/mongodb.js
+++ b/src/repositories/organisations/mongodb.js
@@ -83,7 +83,7 @@ const performUpdate = (db) => async (id, version, updates) => {
     throw Boom.notFound(`Organisation with id ${validatedId} not found`)
   }
 
-  const { status, ...merged } = { ...existing, ...validatedUpdates }
+  const { status: _, ...merged } = { ...existing, ...validatedUpdates }
 
   const registrations = mergeSubcollection(
     existing.registrations,
@@ -131,7 +131,7 @@ const performUpdate = (db) => async (id, version, updates) => {
 
 const performUpsert = (db) => async (organisation) => {
   const validated = validateOrganisationInsert(organisation)
-  const { id, version, schemaVersion, ...updateData } = validated
+  const { id, version: _v, schemaVersion: _s, ...updateData } = validated
 
   const existing = await db
     .collection(COLLECTION_NAME)
@@ -173,7 +173,7 @@ const performFindById =
     let validatedId
     try {
       validatedId = validateId(id)
-    } catch (error) {
+    } catch (_error) {
       throw Boom.notFound(`Organisation with id ${id} not found`)
     }
 
diff --git a/src/repositories/summary-logs/contract/test-data.js b/src/repositories/summary-logs/contract/test-data.js
index bc138f9d..86dea5ab 100644
--- a/src/repositories/summary-logs/contract/test-data.js
+++ b/src/repositories/summary-logs/contract/test-data.js
@@ -11,7 +11,7 @@ export const buildFile = (overrides = {}) => ({
 })
 
 export const buildPendingFile = (overrides = {}) => {
-  const { uri, status, ...rest } = overrides
+  const { uri: _u, status: _s, ...rest } = overrides
   return {
     id: generateFileId(),
     name: 'test.xlsx',
@@ -21,7 +21,7 @@ export const buildPendingFile = (overrides = {}) => {
 }
 
 export const buildRejectedFile = (overrides = {}) => {
-  const { uri, status, ...rest } = overrides
+  const { uri: _u, status: _s, ...rest } = overrides
   return {
     id: generateFileId(),
     name: 'test.xlsx',
diff --git a/src/repositories/waste-records/mongodb.js b/src/repositories/waste-records/mongodb.js
index f1404bc4..0a0241eb 100644
--- a/src/repositories/waste-records/mongodb.js
+++ b/src/repositories/waste-records/mongodb.js
@@ -10,7 +10,7 @@ const SCHEMA_VERSION = 1
  * @returns {import('./port.js').WasteRecord} Domain waste record
  */
 const mapDocumentToDomain = (doc) => {
-  const { _id, schemaVersion, ...domainFields } = doc
+  const { _id, schemaVersion: _s, ...domainFields } = doc
   return structuredClone(domainFields)
 }
 
diff --git a/src/repositories/waste-records/validation.test.js b/src/repositories/waste-records/validation.test.js
index d1a924a4..a312759c 100644
--- a/src/repositories/waste-records/validation.test.js
+++ b/src/repositories/waste-records/validation.test.js
@@ -80,28 +80,28 @@ describe('validation', () => {
     })
 
     it('rejects record missing organisationId', () => {
-      const { organisationId, ...invalid } = validRecord
+      const { organisationId: _, ...invalid } = validRecord
       expect(() => validateWasteRecord(invalid)).toThrow(
         /organisationId is required/
       )
     })
 
     it('rejects record missing registrationId', () => {
-      const { registrationId, ...invalid } = validRecord
+      const { registrationId: _, ...invalid } = validRecord
       expect(() => validateWasteRecord(invalid)).toThrow(
         /registrationId is required/
       )
     })
 
     it('rejects record missing rowId', () => {
-      const { rowId, ...invalid } = validRecord
+      const { rowId: _, ...invalid } = validRecord
       expect(() => validateWasteRecord(invalid)).toThrow(
         /Invalid waste record:.*rowId.*is required/
       )
     })
 
     it('rejects record missing type', () => {
-      const { type, ...invalid } = validRecord
+      const { type: _, ...invalid } = validRecord
       expect(() => validateWasteRecord(invalid)).toThrow(
         /Invalid waste record:.*type.*is required/
       )
@@ -115,14 +115,14 @@ describe('validation', () => {
     })
 
     it('rejects record missing data', () => {
-      const { data, ...invalid } = validRecord
+      const { data: _, ...invalid } = validRecord
       expect(() => validateWasteRecord(invalid)).toThrow(
         /Invalid waste record:.*data.*is required/
       )
     })
 
     it('rejects record missing versions', () => {
-      const { versions, ...invalid } = validRecord
+      const { versions: _, ...invalid } = validRecord
       expect(() => validateWasteRecord(invalid)).toThrow(
         /Invalid waste record:.*versions.*is required/
       )
diff --git a/src/routes/v1/dev/organisations/patch-by-id.js b/src/routes/v1/dev/organisations/patch-by-id.js
index ab981ebd..384b30fd 100644
--- a/src/routes/v1/dev/organisations/patch-by-id.js
+++ b/src/routes/v1/dev/organisations/patch-by-id.js
@@ -1,10 +1,9 @@
+import { mergeSubcollection } from '#repositories/organisations/helpers.js'
 import Boom from '@hapi/boom'
 import { StatusCodes } from 'http-status-codes'
 import Joi from 'joi'
 import mergeWith from 'lodash.mergewith'
 
-import { mergeSubcollection } from '#repositories/organisations/helpers.js'
-
 /** @import {Organisation} from '#domain/organisations/model.js' */
 /** @import {OrganisationsRepository} from '#repositories/organisations/port.js' */
 
diff --git a/src/routes/v1/organisations/registrations/summary-logs/submit/post.test.js b/src/routes/v1/organisations/registrations/summary-logs/submit/post.test.js
index 1d2fe69f..21ac68d2 100644
--- a/src/routes/v1/organisations/registrations/summary-logs/submit/post.test.js
+++ b/src/routes/v1/organisations/registrations/summary-logs/submit/post.test.js
@@ -38,7 +38,7 @@ describe(`${summaryLogsSubmitPath} route`, () => {
 
     server = await createTestServer({
       repositories: {
-        summaryLogsRepository: (logger) => summaryLogsRepository
+        summaryLogsRepository: (_logger) => summaryLogsRepository
       },
       workers: {
         summaryLogsWorker
diff --git a/src/routes/v1/organisations/registrations/summary-logs/upload-completed/post.test.js b/src/routes/v1/organisations/registrations/summary-logs/upload-completed/post.test.js
index ca54f528..66dc1ceb 100644
--- a/src/routes/v1/organisations/registrations/summary-logs/upload-completed/post.test.js
+++ b/src/routes/v1/organisations/registrations/summary-logs/upload-completed/post.test.js
@@ -5,10 +5,10 @@ import {
   UPLOAD_STATUS
 } from '#domain/summary-logs/status.js'
 import { createInMemoryFeatureFlags } from '#feature-flags/feature-flags.inmemory.js'
-import { createTestServer } from '#test/create-test-server.js'
 import { createInMemorySummaryLogsRepository } from '#repositories/summary-logs/inmemory.js'
-import { setupAuthContext } from '#vite/helpers/setup-auth-mocking.js'
+import { createTestServer } from '#test/create-test-server.js'
 import { entraIdMockAuthTokens } from '#vite/helpers/create-entra-id-test-tokens.js'
+import { setupAuthContext } from '#vite/helpers/setup-auth-mocking.js'
 
 import { summaryLogsUploadCompletedPath } from './post.js'
 
@@ -113,7 +113,7 @@ describe(`${summaryLogsUploadCompletedPath} route`, () => {
 
     server = await createTestServer({
       repositories: {
-        summaryLogsRepository: (logger) => summaryLogsRepository
+        summaryLogsRepository: (_logger) => summaryLogsRepository
       },
       workers: {
         summaryLogsWorker
diff --git a/src/workers/summary-logs/worker/integration.test.js b/src/workers/summary-logs/worker/integration.test.js
index e8ee9836..7d45984e 100644
--- a/src/workers/summary-logs/worker/integration.test.js
+++ b/src/workers/summary-logs/worker/integration.test.js
@@ -1,17 +1,21 @@
+/** @import {SummaryLogExtractor} from '#domain/summary-logs/extractor/port.js' */
+/** @import {MetadataEntry} from '#domain/summary-logs/extractor/port.js' */
+/** @import {WasteProcessingTypeValue} from '#domain/organisations/model.js' */
+
 import { randomUUID } from 'crypto'
 
 import { createInMemorySummaryLogExtractor } from '#application/summary-logs/extractor-inmemory.js'
 import { createSummaryLogsValidator } from '#application/summary-logs/validate.js'
-import { createInMemoryWasteRecordsRepository } from '#repositories/waste-records/inmemory.js'
 import { logger } from '#common/helpers/logging/logger.js'
 import {
   SUMMARY_LOG_STATUS,
   UPLOAD_STATUS
 } from '#domain/summary-logs/status.js'
-import { createInMemorySummaryLogsRepository } from '#repositories/summary-logs/inmemory.js'
-import { waitForVersion } from '#repositories/summary-logs/contract/test-helpers.js'
-import { createInMemoryOrganisationsRepository } from '#repositories/organisations/inmemory.js'
 import { buildOrganisation } from '#repositories/organisations/contract/test-data.js'
+import { createInMemoryOrganisationsRepository } from '#repositories/organisations/inmemory.js'
+import { waitForVersion } from '#repositories/summary-logs/contract/test-helpers.js'
+import { createInMemorySummaryLogsRepository } from '#repositories/summary-logs/inmemory.js'
+import { createInMemoryWasteRecordsRepository } from '#repositories/waste-records/inmemory.js'
 
 describe('SummaryLogsValidator integration', () => {
   let summaryLogsRepository
@@ -77,6 +81,16 @@ describe('SummaryLogsValidator integration', () => {
     }
   }
 
+  /**
+   * @typedef {{
+   *  registrationType: WasteProcessingTypeValue;
+   *  registrationWRN: string;
+   *  accreditationNumber?: string;
+   *  metadata?: Record<string, MetadataEntry>;
+   *  summaryLogExtractor?: SummaryLogExtractor;
+   * }} RunValidationParams
+   * @param {RunValidationParams} params
+   */
   const runValidation = async ({
     registrationType,
     registrationWRN,
@@ -277,23 +291,16 @@ describe('SummaryLogsValidator integration', () => {
       {
         registrationType: 'reprocessor',
         registrationWRN: 'REG-123',
-        spreadsheetType: 'EXPORTER',
-        expectedWasteProcessingType: 'exporter'
+        spreadsheetType: 'EXPORTER'
       },
       {
         registrationType: 'exporter',
         registrationWRN: 'REG-456',
-        spreadsheetType: 'REPROCESSOR_INPUT',
-        expectedWasteProcessingType: 'reprocessor'
+        spreadsheetType: 'REPROCESSOR_INPUT'
       }
     ])(
       'when $spreadsheetType type does not match $registrationType registration',
-      ({
-        registrationType,
-        registrationWRN,
-        spreadsheetType,
-        expectedWasteProcessingType
-      }) => {
+      ({ registrationType, registrationWRN, spreadsheetType }) => {
         it('should fail validation with mismatch error', async () => {
           const { updated, summaryLog } = await runValidation({
             registrationType,