diff --git a/apps/self-service/src/app/registration/registration-page.html b/apps/self-service/src/app/registration/registration-page.html
index 255dba4..e91cc80 100644
--- a/apps/self-service/src/app/registration/registration-page.html
+++ b/apps/self-service/src/app/registration/registration-page.html
@@ -14,10 +14,8 @@
         @if (documentsProvided()) {
           <p utrecht-paragraph role="status">Uw documenten zijn aangeleverd.</p>
         } @else {
-          @if (provideDocumentsFailed()) {
-            <p utrecht-paragraph role="alert">
-              Het aanleveren van uw documenten is niet gelukt. Probeer het opnieuw.
-            </p>
+          @if (provideDocumentsError(); as error) {
+            <p utrecht-paragraph role="alert">{{ error }}</p>
           }
           <p utrecht-paragraph>Lever uw diploma aan (PDF).</p>
           <label utrecht-form-label for="diploma">Diploma</label>
diff --git a/apps/self-service/src/app/registration/registration-page.ts b/apps/self-service/src/app/registration/registration-page.ts
index b225ba3..dfb0670 100644
--- a/apps/self-service/src/app/registration/registration-page.ts
+++ b/apps/self-service/src/app/registration/registration-page.ts
@@ -1,5 +1,6 @@
 import { Component, inject, type OnInit, signal } from '@angular/core';
-import { BffApiV1Service, type CurrentRegistration, type SubmitAccepted } from 'api-client';
+import { HttpErrorResponse } from '@angular/common/http';
+import { BffApiV1Service, type CurrentRegistration, type Refusal, type SubmitAccepted } from 'api-client';
 import { AuthService } from 'auth';
 import { UtrechtComponentsModule } from 'ui';
 
@@ -31,7 +32,8 @@ export class RegistrationPage implements OnInit {
   protected readonly withdrawFailed = signal(false);
   protected readonly providingDocuments = signal(false);
   protected readonly documentsProvided = signal(false);
-  protected readonly provideDocumentsFailed = signal(false);
+  /** Why the last upload failed, worded for the citizen; undefined while there is nothing to report. */
+  protected readonly provideDocumentsError = signal<string | undefined>(undefined);
   protected readonly selectedFile = signal<File | undefined>(undefined);
 
   /** Resume an existing in-flight registration after a refresh (S-26): the BFF returns the caller's
@@ -80,12 +82,12 @@ export class RegistrationPage implements OnInit {
       return;
     }
     this.providingDocuments.set(true);
-    this.provideDocumentsFailed.set(false);
+    this.provideDocumentsError.set(undefined);
     let contentBase64: string;
     try {
       contentBase64 = await readAsBase64(file);
     } catch {
-      this.provideDocumentsFailed.set(true);
+      this.provideDocumentsError.set(uploadFailure());
       this.providingDocuments.set(false);
       return;
     }
@@ -101,8 +103,8 @@ export class RegistrationPage implements OnInit {
           this.providingDocuments.set(false);
         },
         // Surface the failure instead of swallowing it: keep the action so the user can retry.
-        error: () => {
-          this.provideDocumentsFailed.set(true);
+        error: (err: unknown) => {
+          this.provideDocumentsError.set(uploadFailure(err));
           this.providingDocuments.set(false);
         },
       });
@@ -129,6 +131,20 @@ export class RegistrationPage implements OnInit {
   }
 }
 
+/** Word a failed upload for the citizen: the BFF says why a file was refused (422 + reason) or that
+ *  the virus scanner was unreachable (503, S-29); anything else is a generic retry. */
+function uploadFailure(err?: unknown): string {
+  if (err instanceof HttpErrorResponse && err.status === 422) {
+    return (err.error as Refusal | null)?.reason === 'infected'
+      ? 'Er is een virus gevonden in dit bestand. Het is niet opgeslagen; lever een ander bestand aan.'
+      : 'Dit bestand is geen PDF. Lever uw diploma aan als PDF-bestand.';
+  }
+  if (err instanceof HttpErrorResponse && err.status === 503) {
+    return 'Uw bestand kan tijdelijk niet worden gecontroleerd. Probeer het later opnieuw.';
+  }
+  return 'Het aanleveren van uw documenten is niet gelukt. Probeer het opnieuw.';
+}
+
 /** Read a file's bytes as a base64 string (without the `data:...;base64,` prefix). */
 function readAsBase64(file: File): Promise<string> {
   return new Promise<string>((resolve, reject) => {