2012/9/3 André Costa <lokal_profil@hotmail.com>
I found that writing a comment in the id field label of the upload wizard drastically reduced the number of incorrect id's last year. See e.g. https://commons.wikimedia.org/wiki/MediaWiki:Mwe-upwiz-campaigns-wlm-se-bbr-id/en

So assuming your id's always take a similar format you could just say something like "should be numbers and look like XX-XXX-XXXX"
 
I'd like to do this to the colombian wizard. Can someone who can edit https://commons.wikimedia.org/wiki/MediaWiki:Mwe-upwiz-campaigns-wlm-co-id/es help me with that? The new text would be "Código del monumento (ver las listas; son 5 dígitos: XX-XXX)".

Thanks.