I did a quick search but didn't really find anything, so I look to you all.

I have a package to send out via USPS. I have a box from Amazon that wil work perfectly. Do I have to wrap it in brown paper or obliterate the Amazon swoop "arrows" or other identifying marks before bringing it down to the post office or can I use it as is?

Use it. Scribble through any bar codes if you must.

It's just advertising.
I just run a permanent marker across the old bar codes.
You're really only concerned with the eyes of the bar code scanner.

Or, cut one corner, turn it inside out and re-use it.

Thanks, all. It's just going to family. Permanent marker is poised and ready for action.

shoot, I reuse boxes like that all the time. I've even sent boxes with the UPS sticker still on them through the USPS. As mentioned above, they just told me to run a permanent marker across any barcodes.

[www.usps.com]

Thanks, tronnei. I even searched the USPS site, because I thought I had seen info there in the past. Couldn't find it this time, though.