diff --git a/lib/api/consumers/format-to-legacy-helpers.js b/lib/api/consumers/format-to-legacy-helpers.js
index 473b8811..b88712ca 100644
--- a/lib/api/consumers/format-to-legacy-helpers.js
+++ b/lib/api/consumers/format-to-legacy-helpers.js
@@ -107,15 +107,7 @@ export const formatCommonToponymDataForLegacy = (commonToponym, district, pseudo
   const codeAncienneCommune = meta?.bal?.codeAncienneCommune
   const legacyCommonToponymFantoirId = meta?.dgfip?.fantoir ? `${cog}_${meta?.dgfip?.fantoir}` : null
 
-  let legacyCommonToponymId = legacyCommonToponymFantoirId
-  // If the legacy common toponym id is already used or not defined, we calculate a pseudo code
-  if (!legacyCommonToponymId || commonToponymLegacyIDSet.has(legacyCommonToponymId)) {
-    legacyCommonToponymId = `${cog}_${pseudoCodeVoieGenerator.getCode(legacyLabelValue, codeAncienneCommune)}`.toLowerCase()
-    // If the pseudo code is already used, we generate a new one with a hash from the common toponym id
-    if (commonToponymLegacyIDSet.has(legacyCommonToponymId)) {
-      legacyCommonToponymId = `${cog}_${createHmac('sha256', 'ban').update(id).digest('hex').slice(0, 6)}`
-    }
-  }
+  const legacyCommonToponymId = getLegacyCommonToponymId(commonToponymLegacyIDSet, legacyCommonToponymFantoirId, meta, {cog, id, pseudoCodeVoieGenerator, legacyLabelValue, codeAncienneCommune})
 
   // Store the legacy common toponym id for each common toponym to then be able to set it on legacy addresses
   commonToponymLegacyIDCommonToponymIDMap.set(id, legacyCommonToponymId)
@@ -212,7 +204,7 @@ export const formatAddressDataForLegacy = (address, district, commonToponymLegac
 
   // Ids
   const legacyCommonToponymId = commonToponymLegacyIDCommonToponymIDMap.get(mainCommonToponymID)
-  const legacyInteropKey = `${legacyCommonToponymId}_${String(number).padStart(5, '0')}${suffix ? `_${suffix}` : ''}`.toLowerCase()
+  const legacyInteropKey = getAddressLegacyInteropKey(meta, {legacyCommonToponymId, number, suffix})
   const legacyID = getAddressLegacyId(addressLegacyIDSet, legacyInteropKey)
   addressLegacyIDSet.add(legacyID)
   const banIdSecondaryCommonToponyms = secondaryCommonToponymIDs && secondaryCommonToponymIDs.length > 0 ? secondaryCommonToponymIDs : null
@@ -332,3 +324,70 @@ const getAddressLegacyId = (addressLegacyIDSet, legacyInteropKey, suffix = 0) =>
 
   return `${legacyInteropKey}`
 }
+
+const getAddressLegacyInteropKey = (meta, {legacyCommonToponymId, number, suffix}) => {
+  const cleInterop = meta.bal?.cleInterop
+  const isValidInteropKey = checkIfCleInteropIsValid(cleInterop)
+  const addressLegacyInteropKey = isValidInteropKey
+    ? cleInterop
+    : `${legacyCommonToponymId}_${String(number).padStart(5, '0')}${suffix ? `_${suffix}` : ''}`.toLowerCase()
+
+  return addressLegacyInteropKey
+}
+
+const getLegacyCommonToponymId = (
+  commonToponymLegacyIDSet,
+  legacyCommonToponymFantoirId,
+  meta,
+  {cog, id, pseudoCodeVoieGenerator, legacyLabelValue, codeAncienneCommune}
+) => {
+  let legacyCommonToponymId
+  const cleInterop = meta.bal?.cleInterop
+  const isCleInteropValid = checkIfCleInteropIsValid(cleInterop)
+  if (isCleInteropValid) {
+    const lastUnderscoreIndex = cleInterop.lastIndexOf('_')
+    legacyCommonToponymId = cleInterop.slice(0, lastUnderscoreIndex)
+  } else {
+    legacyCommonToponymId = legacyCommonToponymFantoirId
+  }
+
+  // If the legacy common toponym id is already used or not defined, we calculate a pseudo code
+  if (!legacyCommonToponymId || commonToponymLegacyIDSet.has(legacyCommonToponymId)) {
+    legacyCommonToponymId = `${cog}_${pseudoCodeVoieGenerator.getCode(legacyLabelValue, codeAncienneCommune)}`.toLowerCase()
+    // If the pseudo code is already used, we generate a new one with a hash from the common toponym id
+    if (commonToponymLegacyIDSet.has(legacyCommonToponymId)) {
+      legacyCommonToponymId = `${cog}_${createHmac('sha256', 'ban').update(id).digest('hex').slice(0, 6)}`
+    }
+  }
+
+  return legacyCommonToponymId
+}
+
+const checkIfCleInteropIsValid = cleInterop => {
+  if (!cleInterop) {
+    return false
+  }
+
+  // https://aitf-sig-topo.github.io/voies-adresses/files/AITF_SIG_Topo_Format_Base_Adresse_Locale_v1.3.pdf
+  // ● INSEE code with 5 characters
+  // ● Street code: the unique street identifier provided by the national unique service,
+  //   or the FANTOIR DGFiP code, consisting of 4 to 6 alphanumeric characters
+  // ● Address number consisting of 5 characters, prefixed with zeros if necessary
+  // ● Suffix (bis / ter / qua / qui / a / b / c...). The repetition indices “bis, ter…” will
+  //   be coded with 3 characters, and others (a, b, c, a1, b2...) will be in lowercase
+  //   without a fixed number of characters.
+  // ● Each item is separated by an underscore “_”
+  // ● Everything is in lowercase
+
+  const cleInteropFormatRegex = /^\d{5}_[a-z\d]{4,6}_\d{5}(_[a-z]{3}|_[a-z])?(_[a-z])*$/
+  if (!cleInteropFormatRegex.test(cleInterop)) {
+    return false
+  }
+
+  // Check if the street code is 'xxxx' to detect the non-valid pseudo code created by mes-adresses
+  if (cleInterop.split('_')[1] === 'xxxx') {
+    return false
+  }
+
+  return true
+}