diff --git a/frontend/pages/incomingInvoices/[mode]/[id].vue b/frontend/pages/incomingInvoices/[mode]/[id].vue
index 6851d05..bf4c50b 100644
--- a/frontend/pages/incomingInvoices/[mode]/[id].vue
+++ b/frontend/pages/incomingInvoices/[mode]/[id].vue
@@ -7,6 +7,7 @@ import { useDraggable } from '@vueuse/core'
 const dataStore = useDataStore()
 const route = useRoute()
 const mode = ref(route.params.mode)
+const toast = useToast()
 
 // --- Page Leave Logic ---
 const isModified = ref(false) // Speichert, ob Änderungen vorgenommen wurden
@@ -119,6 +120,7 @@ const totalCalculated = computed(() => {
 })
 
 const hasAmount = (value) => value !== null && value !== undefined && value !== ""
+const hasValidNumber = (value) => hasAmount(value) && Number.isFinite(Number(value))
 
 const recalculateItem = (item, source) => {
   const taxRate = Number(taxOptions.value.find(i => i.key === item.taxType)?.percentage || 0);
@@ -151,6 +153,15 @@ const moveGrossToNet = (item) => {
 
 // --- Saving ---
 const updateIncomingInvoice = async (setBooked = false) => {
+  if (setBooked && hasBlockingIncomingInvoiceErrors.value) {
+    toast.add({
+      title: "Buchen nicht möglich",
+      description: "Bitte beheben Sie zuerst die rot markierten Pflichtfehler.",
+      color: "rose"
+    })
+    return
+  }
+
   let item = { ...itemInfo.value }
   delete item.files
   item.state = setBooked ? "Gebucht" : "Entwurf"
@@ -162,20 +173,32 @@ const updateIncomingInvoice = async (setBooked = false) => {
 }
 
 const findIncomingInvoiceErrors = computed(() => {
-  let errors = []
+  const errors = []
   const i = itemInfo.value
 
   if(!i.vendor) errors.push({message: "Es ist kein Lieferant ausgewählt", type: "breaking"})
-  if(!i.reference) errors.push({message: "Es ist keine Referenz angegeben", type: "breaking"})
+  if(!i.reference || !String(i.reference).trim()) errors.push({message: "Es ist keine Referenz angegeben", type: "breaking"})
   if(!i.date) errors.push({message: "Es ist kein Datum ausgewählt", type: "breaking"})
+  if(!i.accounts || i.accounts.length === 0) errors.push({message: "Es ist keine Position vorhanden", type: "breaking"})
 
   i.accounts.forEach((account, idx) => {
     if(!account.account) errors.push({message: `Pos ${idx+1}: Keine Kategorie`, type: "breaking"})
-    if(account.amountNet === null) errors.push({message: `Pos ${idx+1}: Kein Betrag`, type: "breaking"})
+    if(!hasValidNumber(account.amountNet) && !hasValidNumber(account.amountGross)) {
+      errors.push({message: `Pos ${idx+1}: Kein gültiger Betrag`, type: "breaking"})
+    }
+    if(!account.taxType) errors.push({message: `Pos ${idx+1}: Kein Steuerschlüssel`, type: "breaking"})
+    if(hasValidNumber(account.amountNet) && !hasValidNumber(account.amountTax)) {
+      errors.push({message: `Pos ${idx+1}: Steuerbetrag fehlt, bitte Steuer neu berechnen`, type: "warning"})
+    }
   })
 
-  return errors.sort((a,b) => (a.type === "breaking") ? -1 : 1)
+  const order = { breaking: 0, warning: 1 }
+  return errors.sort((a,b) => order[a.type] - order[b.type])
 })
+
+const blockingIncomingInvoiceErrors = computed(() => findIncomingInvoiceErrors.value.filter(i => i.type === "breaking"))
+const warningIncomingInvoiceErrors = computed(() => findIncomingInvoiceErrors.value.filter(i => i.type === "warning"))
+const hasBlockingIncomingInvoiceErrors = computed(() => blockingIncomingInvoiceErrors.value.length > 0)
 </script>
 
 <template>
@@ -208,7 +231,7 @@ const findIncomingInvoiceErrors = computed(() => {
       <UButton
           v-if="mode !== 'show'"
           @click="updateIncomingInvoice(true)"
-          :disabled="findIncomingInvoiceErrors.filter(i => i.type === 'breaking').length > 0"
+          :disabled="hasBlockingIncomingInvoiceErrors"
       >
         Speichern & Buchen
       </UButton>
@@ -263,14 +286,35 @@ const findIncomingInvoiceErrors = computed(() => {
           <UAlert
               v-if="findIncomingInvoiceErrors.length > 0"
               title="Prüfung erforderlich"
-              :color="findIncomingInvoiceErrors.some(i => i.type === 'breaking') ? 'rose' : 'orange'"
+              :color="hasBlockingIncomingInvoiceErrors ? 'rose' : 'orange'"
               variant="soft"
               icon="i-heroicons-exclamation-triangle"
           >
             <template #description>
-              <ul class="list-disc list-inside text-sm mt-1">
-                <li v-for="(err, idx) in findIncomingInvoiceErrors" :key="idx">{{ err.message }}</li>
-              </ul>
+              <div class="space-y-3 text-sm mt-1">
+                <div v-if="blockingIncomingInvoiceErrors.length > 0">
+                  <p class="font-semibold text-rose-700 dark:text-rose-300">Pflichtfehler</p>
+                  <ul class="list-disc list-inside mt-1">
+                    <li
+                        v-for="(err, idx) in blockingIncomingInvoiceErrors"
+                        :key="`blocking-${idx}-${err.message}`"
+                    >
+                      {{ err.message }}
+                    </li>
+                  </ul>
+                </div>
+                <div v-if="warningIncomingInvoiceErrors.length > 0">
+                  <p class="font-semibold text-orange-700 dark:text-orange-300">Hinweise</p>
+                  <ul class="list-disc list-inside mt-1">
+                    <li
+                        v-for="(err, idx) in warningIncomingInvoiceErrors"
+                        :key="`warning-${idx}-${err.message}`"
+                    >
+                      {{ err.message }}
+                    </li>
+                  </ul>
+                </div>
+              </div>
             </template>
           </UAlert>