diff --git a/src/server/plugins/engine/pageControllers/helpers/submission.test.ts b/src/server/plugins/engine/pageControllers/helpers/submission.test.ts
index d72ef6258..c17a7aacc 100644
--- a/src/server/plugins/engine/pageControllers/helpers/submission.test.ts
+++ b/src/server/plugins/engine/pageControllers/helpers/submission.test.ts
@@ -284,6 +284,36 @@ describe('Submission helpers', () => {
         }
       ])
     })
+
+    it('should send empty string for optional GeospatialField', () => {
+      const mockGeospatialField = Object.create(
+        GeospatialField.prototype
+      ) as GeospatialField
+      mockGeospatialField.name = 'geospatial'
+      mockGeospatialField.options = { required: false }
+
+      const items = [
+        {
+          name: 'geospatial',
+          label: 'Site features',
+          field: mockGeospatialField,
+          state: {
+            geospatial: undefined
+          } as FormSubmissionState
+        }
+      ] as unknown as DetailItemField[]
+
+      const result = buildMainRecords(items)
+
+      expect(result).toHaveLength(1)
+      expect(result).toEqual([
+        {
+          name: 'geospatial',
+          title: 'Site features',
+          value: ''
+        }
+      ])
+    })
   })
 
   describe('buildRepeaterRecords', () => {
@@ -383,5 +413,51 @@ describe('Submission helpers', () => {
         }
       ])
     })
+
+    it('should send empty string for optional GeospatialField', () => {
+      const mockGeospatialField = Object.create(
+        GeospatialField.prototype
+      ) as GeospatialField
+      mockGeospatialField.name = 'geospatial'
+      mockGeospatialField.options = { required: false }
+
+      const items = [
+        {
+          name: 'features',
+          label: 'Site features repeater',
+          subItems: [
+            [
+              {
+                name: 'geospatial',
+                label: 'Site features',
+                field: mockGeospatialField,
+                state: {
+                  geospatial: undefined
+                } as FormSubmissionState
+              } as unknown as DetailItemField[]
+            ]
+          ]
+        }
+      ] as unknown as DetailItemField[]
+
+      const result = buildRepeaterRecords(items)
+
+      expect(result).toHaveLength(1)
+      expect(result).toEqual([
+        {
+          name: 'features',
+          title: 'Site features repeater',
+          value: [
+            [
+              {
+                name: 'geospatial',
+                title: 'Site features',
+                value: ''
+              }
+            ]
+          ]
+        }
+      ])
+    })
   })
 })
diff --git a/src/server/plugins/engine/pageControllers/helpers/submission.ts b/src/server/plugins/engine/pageControllers/helpers/submission.ts
index 34810bdd8..f2974d2ec 100644
--- a/src/server/plugins/engine/pageControllers/helpers/submission.ts
+++ b/src/server/plugins/engine/pageControllers/helpers/submission.ts
@@ -36,10 +36,11 @@ export function buildMainRecords(items: DetailItem[]): SubmitRecord[] {
     } else if (item.field instanceof GeospatialField) {
       // Stringify of GeoJSON is done here rather than inside `getContextValueFromState`
       // so we don't incur the overhead of JSON.stringify on every request when building context
+      const value = item.field.getFormValueFromState(item.state)
       records.push({
         name: item.name,
         title: item.label,
-        value: JSON.stringify(item.field.getFormValueFromState(item.state))
+        value: value === undefined ? '' : JSON.stringify(value)
       })
     } else {
       records.push({
@@ -109,18 +110,24 @@ export function buildRepeaterRecords(
       name: item.name,
       title: item.label,
       value: item.subItems.map((detailItems) =>
-        detailItems.map((subItem) => ({
-          name: subItem.name,
-          title: subItem.label,
-          value:
+        detailItems.map((subItem) => {
+          let value
+
+          if (subItem.field instanceof GeospatialField) {
             // Stringify of GeoJSON is done here rather than inside `getContextValueFromState`
             // so we don't incur the overhead of JSON.stringify on every request when building context
-            subItem.field instanceof GeospatialField
-              ? JSON.stringify(
-                  subItem.field.getFormValueFromState(subItem.state)
-                )
-              : getAnswer(subItem.field, subItem.state, { format: 'data' })
-        }))
+            const formValue = subItem.field.getFormValueFromState(subItem.state)
+            value = formValue === undefined ? '' : JSON.stringify(formValue)
+          } else {
+            value = getAnswer(subItem.field, subItem.state, { format: 'data' })
+          }
+
+          return {
+            name: subItem.name,
+            title: subItem.label,
+            value
+          }
+        })
       )
     }))
 }