Julie here from Shopify Support.
While a utility bill is an ideal proof of address, our Shopify Payments team recognizes that not everyone pays utilities. In this case, you can simply upload any pertinent document that would provide a proof of address associated with the one you used when you first signed up. Just make sure to leave a note in the comments section indicating why you are unable to provide a copy of a utility bill.
As a side note, you should also have received an email from us about your Shopify Payments account. If you have any questions about the documents you should be uploading, then I suggest responding to that email. Your response will go straight into the inbox of the Shopify Payments team, who is best equipped to answer any questions about the process.
I hope this clears things up!