diff --git a/app/presenters/bill-runs/setup/create.presenter.js b/app/presenters/bill-runs/setup/create.presenter.js
index 6c46876d91..7ebc517cf7 100644
--- a/app/presenters/bill-runs/setup/create.presenter.js
+++ b/app/presenters/bill-runs/setup/create.presenter.js
@@ -54,7 +54,7 @@ function go (session, billRun) {
 }
 
 function _backLink (session) {
-  const { type, year } = session.data
+  const { type, year } = session
 
   if (!type.startsWith('two_part')) {
     return `/system/bill-runs/setup/${session.id}/region`
diff --git a/app/presenters/bill-runs/setup/region.presenter.js b/app/presenters/bill-runs/setup/region.presenter.js
index 607e0c55d1..c2be29a81e 100644
--- a/app/presenters/bill-runs/setup/region.presenter.js
+++ b/app/presenters/bill-runs/setup/region.presenter.js
@@ -17,7 +17,7 @@ function go (session, regions) {
   return {
     sessionId: session.id,
     regions,
-    selectedRegion: session.data.region ? session.data.region : null
+    selectedRegion: session.region ? session.region : null
   }
 }
 
diff --git a/app/presenters/bill-runs/setup/season.presenter.js b/app/presenters/bill-runs/setup/season.presenter.js
index 5713498191..f66f23af8a 100644
--- a/app/presenters/bill-runs/setup/season.presenter.js
+++ b/app/presenters/bill-runs/setup/season.presenter.js
@@ -15,7 +15,7 @@
 function go (session) {
   return {
     sessionId: session.id,
-    selectedSeason: session.data.season ? session.data.season : null
+    selectedSeason: session.season ? session.season : null
   }
 }
 
diff --git a/app/presenters/bill-runs/setup/type.presenter.js b/app/presenters/bill-runs/setup/type.presenter.js
index 0612f7c69a..60668d1f12 100644
--- a/app/presenters/bill-runs/setup/type.presenter.js
+++ b/app/presenters/bill-runs/setup/type.presenter.js
@@ -15,7 +15,7 @@
 function go (session) {
   return {
     sessionId: session.id,
-    selectedType: session.data.type ? session.data.type : null
+    selectedType: session.type ? session.type : null
   }
 }
 
diff --git a/app/presenters/bill-runs/setup/year.presenter.js b/app/presenters/bill-runs/setup/year.presenter.js
index b1845a2f37..d2186a0a33 100644
--- a/app/presenters/bill-runs/setup/year.presenter.js
+++ b/app/presenters/bill-runs/setup/year.presenter.js
@@ -15,7 +15,7 @@
 function go (session) {
   return {
     sessionId: session.id,
-    selectedYear: session.data.year ? session.data.year : null
+    selectedYear: session.year ? session.year : null
   }
 }
 
diff --git a/app/services/bill-runs/setup/create.service.js b/app/services/bill-runs/setup/create.service.js
index 90f24e3c95..eda6ce4a30 100644
--- a/app/services/bill-runs/setup/create.service.js
+++ b/app/services/bill-runs/setup/create.service.js
@@ -25,7 +25,7 @@ const StartBillRunProcessService = require('../start-bill-run-process.service.js
  */
 async function go (user, existsResults) {
   const { matchResults, session, yearToUse } = existsResults
-  const { region: regionId, type, summer } = session.data
+  const { region: regionId, type, summer } = session
 
   const existingBillRun = matchResults[0]
 
diff --git a/app/services/bill-runs/setup/exists.service.js b/app/services/bill-runs/setup/exists.service.js
index 16ba6a12fd..3434b4e3fe 100644
--- a/app/services/bill-runs/setup/exists.service.js
+++ b/app/services/bill-runs/setup/exists.service.js
@@ -38,7 +38,7 @@ const SessionModel = require('../../../models/session.model.js')
 async function go (sessionId) {
   const session = await SessionModel.query().findById(sessionId)
 
-  const { region, type, year } = session.data
+  const { region, type, year } = session
   const yearToUse = await DetermineFinancialYearEndService.go(region, type, year)
 
   const matchResults = await _fetchMatchingBillRun(session, yearToUse)
@@ -54,13 +54,13 @@ async function go (sessionId) {
 }
 
 async function _fetchMatchingBillRun (session, year) {
-  const { region, season, type } = session.data
+  const { region, season, type } = session
 
   return DetermineBlockingBillRunService.go(region, type, year, season)
 }
 
 function _pageData (session, matchResults) {
-  const { type } = session.data
+  const { type } = session
 
   // No matches so we can create the bill run
   if (matchResults.length === 0) {
diff --git a/app/services/bill-runs/setup/submit-region.service.js b/app/services/bill-runs/setup/submit-region.service.js
index 4360e3e480..2a6ecfb0e3 100644
--- a/app/services/bill-runs/setup/submit-region.service.js
+++ b/app/services/bill-runs/setup/submit-region.service.js
@@ -40,7 +40,7 @@ async function go (sessionId, payload) {
     await _save(session, payload)
 
     // The journey is complete (we don't need any details) if the bill run type is not 2PT
-    return { setupComplete: !session.data.type.startsWith('two_part') }
+    return { setupComplete: !session.type.startsWith('two_part') }
   }
 
   const formattedData = RegionPresenter.go(session, regions)
@@ -52,7 +52,7 @@ async function go (sessionId, payload) {
 }
 
 async function _save (session, payload) {
-  const currentData = session.data
+  const currentData = session
 
   currentData.region = payload.region
 
diff --git a/app/services/bill-runs/setup/submit-season.service.js b/app/services/bill-runs/setup/submit-season.service.js
index bce40eac53..7d7343fe94 100644
--- a/app/services/bill-runs/setup/submit-season.service.js
+++ b/app/services/bill-runs/setup/submit-season.service.js
@@ -48,11 +48,9 @@ async function go (sessionId, payload) {
 }
 
 async function _save (session, payload) {
-  const currentData = session.data
+  session.season = payload.season
 
-  currentData.season = payload.season
-
-  return session.$query().patch({ data: currentData })
+  return session.$update()
 }
 
 function _validate (payload) {
diff --git a/app/services/bill-runs/setup/submit-type.service.js b/app/services/bill-runs/setup/submit-type.service.js
index a7139bf4ac..f8398ca464 100644
--- a/app/services/bill-runs/setup/submit-type.service.js
+++ b/app/services/bill-runs/setup/submit-type.service.js
@@ -48,11 +48,9 @@ async function go (sessionId, payload) {
 }
 
 async function _save (session, payload) {
-  const currentData = session.data
+  session.type = payload.type
 
-  currentData.type = payload.type
-
-  return session.$query().patch({ data: currentData })
+  return session.$update()
 }
 
 function _validate (payload) {
diff --git a/app/services/bill-runs/setup/submit-year.service.js b/app/services/bill-runs/setup/submit-year.service.js
index 45aa7d78af..85083760c3 100644
--- a/app/services/bill-runs/setup/submit-year.service.js
+++ b/app/services/bill-runs/setup/submit-year.service.js
@@ -37,7 +37,7 @@ async function go (sessionId, payload) {
   if (!validationResult) {
     await _save(session, payload)
 
-    return { setupComplete: ['2024', '2023'].includes(session.data.year) }
+    return { setupComplete: ['2024', '2023'].includes(session.year) }
   }
 
   const formattedData = YearPresenter.go(session)
@@ -49,11 +49,9 @@ async function go (sessionId, payload) {
 }
 
 async function _save (session, payload) {
-  const currentData = session.data
+  session.year = payload.year
 
-  currentData.year = payload.year
-
-  return session.$query().patch({ data: currentData })
+  return session.$update()
 }
 
 function _validate (payload, regions) {
diff --git a/test/presenters/bill-runs/setup/create.presenter.test.js b/test/presenters/bill-runs/setup/create.presenter.test.js
index 0208d4ff02..6a754f1c69 100644
--- a/test/presenters/bill-runs/setup/create.presenter.test.js
+++ b/test/presenters/bill-runs/setup/create.presenter.test.js
@@ -18,7 +18,7 @@ describe('Bill Runs Setup Create presenter', () => {
     beforeEach(() => {
       session = {
         id: '98ad3a1f-8e4f-490a-be05-0aece6755466',
-        data: { type: 'annual' }
+        type: 'annual'
       }
 
       matchingBillRun = {
@@ -55,7 +55,7 @@ describe('Bill Runs Setup Create presenter', () => {
     describe("the 'backLink' property", () => {
       describe("when the selected bill run type is not 'two_part_tariff'", () => {
         beforeEach(() => {
-          session.data.type = 'supplementary'
+          session.type = 'supplementary'
         })
 
         it('returns a link to the region page', () => {
@@ -67,12 +67,12 @@ describe('Bill Runs Setup Create presenter', () => {
 
       describe("when the selected bill run type is 'two_part_tariff'", () => {
         beforeEach(() => {
-          session.data.type = 'two_part_tariff'
+          session.type = 'two_part_tariff'
         })
 
         describe('and the selected financial year is in the SROC period', () => {
           beforeEach(() => {
-            session.data.year = '2023'
+            session.year = '2023'
           })
 
           it('returns a link to the financial year page', () => {
@@ -84,7 +84,7 @@ describe('Bill Runs Setup Create presenter', () => {
 
         describe('and the selected financial year is in the PRESROC period', () => {
           beforeEach(() => {
-            session.data.year = '2022'
+            session.year = '2022'
           })
 
           it('returns a link to the season page', () => {
diff --git a/test/presenters/bill-runs/setup/region.presenter.test.js b/test/presenters/bill-runs/setup/region.presenter.test.js
index b19b8203da..364af313f2 100644
--- a/test/presenters/bill-runs/setup/region.presenter.test.js
+++ b/test/presenters/bill-runs/setup/region.presenter.test.js
@@ -41,7 +41,7 @@ describe('Bill Runs Setup Region presenter', () => {
 
     describe('where the user has previously selected a bill run region', () => {
       beforeEach(() => {
-        session.data.region = 'Stormlands'
+        session.region = 'Stormlands'
       })
 
       it('correctly presents the data', () => {
diff --git a/test/presenters/bill-runs/setup/season.presenter.test.js b/test/presenters/bill-runs/setup/season.presenter.test.js
index fc5e0332bc..d6443b84c8 100644
--- a/test/presenters/bill-runs/setup/season.presenter.test.js
+++ b/test/presenters/bill-runs/setup/season.presenter.test.js
@@ -34,7 +34,7 @@ describe('Bill Runs Setup Season presenter', () => {
 
     describe('where the user has previously selected a season', () => {
       beforeEach(() => {
-        session.data.season = 'summer'
+        session.season = 'summer'
       })
 
       it('correctly presents the data', () => {
diff --git a/test/presenters/bill-runs/setup/type.presenter.test.js b/test/presenters/bill-runs/setup/type.presenter.test.js
index 7b5956e93c..e7c736b1f9 100644
--- a/test/presenters/bill-runs/setup/type.presenter.test.js
+++ b/test/presenters/bill-runs/setup/type.presenter.test.js
@@ -34,7 +34,7 @@ describe('Bill Runs Setup Type presenter', () => {
 
     describe('where the user has previously selected a bill run type', () => {
       beforeEach(() => {
-        session.data.type = 'annual'
+        session.type = 'annual'
       })
 
       it('correctly presents the data', () => {
diff --git a/test/presenters/bill-runs/setup/year.presenter.test.js b/test/presenters/bill-runs/setup/year.presenter.test.js
index 667e264c53..53ba68575d 100644
--- a/test/presenters/bill-runs/setup/year.presenter.test.js
+++ b/test/presenters/bill-runs/setup/year.presenter.test.js
@@ -34,7 +34,7 @@ describe('Bill Runs Setup Year presenter', () => {
 
     describe('where the user has previously selected a financial year', () => {
       beforeEach(() => {
-        session.data.year = 2022
+        session.year = 2022
       })
 
       it('correctly presents the data', () => {
diff --git a/test/services/bill-runs/setup/create.service.test.js b/test/services/bill-runs/setup/create.service.test.js
index 7bf023e00f..626e41c7d5 100644
--- a/test/services/bill-runs/setup/create.service.test.js
+++ b/test/services/bill-runs/setup/create.service.test.js
@@ -44,6 +44,10 @@ describe('Bill Runs Setup Create service', () => {
       session = await SessionHelper.add({
         data: { region: '19a027c6-4aad-47d3-80e3-3917a4579a5b', type: 'annual' }
       })
+      // NOTE: We make these additional $afterFind() calls to trigger the hook that would have been called when the
+      // create service queries for the session. The hook elevates properties from `data` onto the session instance
+      // itself. Without this the tests fail though the service works fine.
+      session.$afterFind()
 
       existsResults = { matchResults: [], session, yearToUse: 2024 }
     })
@@ -62,6 +66,7 @@ describe('Bill Runs Setup Create service', () => {
       session = await SessionHelper.add({
         data: { region: '19a027c6-4aad-47d3-80e3-3917a4579a5b', type: 'annual' }
       })
+      session.$afterFind()
 
       existsResults = { matchResults: [], session, yearToUse: 2024 }
     })
@@ -84,6 +89,7 @@ describe('Bill Runs Setup Create service', () => {
       session = await SessionHelper.add({
         data: { region: '19a027c6-4aad-47d3-80e3-3917a4579a5b', type: 'supplementary' }
       })
+      session.$afterFind()
     })
 
     describe('and there were no matching bill runs', () => {
@@ -147,6 +153,7 @@ describe('Bill Runs Setup Create service', () => {
             season: 'summer'
           }
         })
+        session.$afterFind()
 
         existsResults = { matchResults: [], session, yearToUse: 2022 }
       })
@@ -168,6 +175,7 @@ describe('Bill Runs Setup Create service', () => {
             year: 2023
           }
         })
+        session.$afterFind()
 
         existsResults = { matchResults: [], session, yearToUse: 2023 }
       })
diff --git a/test/services/bill-runs/setup/submit-region.service.test.js b/test/services/bill-runs/setup/submit-region.service.test.js
index 9ae00b7e7e..d745dfa597 100644
--- a/test/services/bill-runs/setup/submit-region.service.test.js
+++ b/test/services/bill-runs/setup/submit-region.service.test.js
@@ -58,7 +58,7 @@ describe('Bill Runs Setup Submit Region service', () => {
 
           const refreshedSession = await session.$query()
 
-          expect(refreshedSession.data.region).to.equal('19a027c6-4aad-47d3-80e3-3917a4579a5b')
+          expect(refreshedSession.region).to.equal('19a027c6-4aad-47d3-80e3-3917a4579a5b')
           expect(result.setupComplete).to.be.true()
         })
       })
@@ -73,7 +73,7 @@ describe('Bill Runs Setup Submit Region service', () => {
 
           const refreshedSession = await session.$query()
 
-          expect(refreshedSession.data.region).to.equal('19a027c6-4aad-47d3-80e3-3917a4579a5b')
+          expect(refreshedSession.region).to.equal('19a027c6-4aad-47d3-80e3-3917a4579a5b')
           expect(result.setupComplete).to.be.false()
         })
       })
diff --git a/test/services/bill-runs/setup/submit-season.service.test.js b/test/services/bill-runs/setup/submit-season.service.test.js
index aff5eb7e7c..14450a768a 100644
--- a/test/services/bill-runs/setup/submit-season.service.test.js
+++ b/test/services/bill-runs/setup/submit-season.service.test.js
@@ -37,7 +37,7 @@ describe('Bill Runs Setup Submit Season service', () => {
 
         const refreshedSession = await session.$query()
 
-        expect(refreshedSession.data.season).to.equal('summer')
+        expect(refreshedSession.season).to.equal('summer')
       })
 
       it('returns an empty object (no page data is needed for a redirect)', async () => {
diff --git a/test/services/bill-runs/setup/submit-type.service.test.js b/test/services/bill-runs/setup/submit-type.service.test.js
index 6e477d49c7..fb273b1143 100644
--- a/test/services/bill-runs/setup/submit-type.service.test.js
+++ b/test/services/bill-runs/setup/submit-type.service.test.js
@@ -37,7 +37,7 @@ describe('Bill Runs Setup Submit Type service', () => {
 
         const refreshedSession = await session.$query()
 
-        expect(refreshedSession.data.type).to.equal('annual')
+        expect(refreshedSession.type).to.equal('annual')
       })
 
       it('returns an empty object (no page data is needed for a redirect)', async () => {
diff --git a/test/services/bill-runs/setup/submit-year.service.test.js b/test/services/bill-runs/setup/submit-year.service.test.js
index 0d10a0db68..76c79f5d9c 100644
--- a/test/services/bill-runs/setup/submit-year.service.test.js
+++ b/test/services/bill-runs/setup/submit-year.service.test.js
@@ -38,7 +38,7 @@ describe('Bill Runs Setup Submit Year service', () => {
 
           const refreshedSession = await session.$query()
 
-          expect(refreshedSession.data.year).to.equal('2023')
+          expect(refreshedSession.year).to.equal('2023')
           expect(result.setupComplete).to.be.true()
         })
       })
@@ -55,7 +55,7 @@ describe('Bill Runs Setup Submit Year service', () => {
 
           const refreshedSession = await session.$query()
 
-          expect(refreshedSession.data.year).to.equal('2022')
+          expect(refreshedSession.year).to.equal('2022')
           expect(result.setupComplete).to.be.false()
         })
       })