When the AEAT returns an "Accepted with Errors" status, the decrypted XML will tell you exactly which invoice line failed.
If possible, use offline tools like Notepad++ (with the XML Tools plugin) or a dedicated browser-based decoder that processes data locally in your scripts rather than sending it to a server. Why Do You Need to Decrypt These Files? sii decrypt online
Open your file in a text editor (like Notepad). If you see a long string of random characters (e.g., PHhtbCB2ZXJzaW9u... ), it is . If you see a giant wall of text starting with , it is simply unformatted . 2. Use a Trusted Decoder To decode Base64 SII data: Copy the encoded string. Use a reputable Base64 to XML converter . Paste the code and hit "Decode." 3. Use an XML Formatter When the AEAT returns an "Accepted with Errors"