I do NOT recommend selling through TRR. Read all seller reviews. This a speed selling co trying to cash in on a quick commission. The prices they assign are RIDICULOULOUS at best. They are not there to get you a good price but a fast buck for themselves. They priced a brand new prada bag with a label on at $625. Minus 20% permanent discount, 60% of that, I receive a whopping $312. After 10 days wait of processing and seeing the prices assigned I pulled my items. I was shocked and even more upset. I rather give the cloths to charity or sell them myself. I think it is insiders who buy the best items at dirt cheap prices they assign themselves.
As a buyer just today I receive a wrong item. They were going to research the problem and find the item I purchased, a coat. They sent me a dirty silk top... This is after waiting for 10 days to get the wrong item.
This co is just very bad. Customer service is spotty. Some reps are just dreadful. They sound like this is a summer gig and they got no training, you can never speak to a supervisor, none is ever available,
Read the reviews and decide if you still want to use this co. If you do, you will be disappointed,

You should fill the box with rocks, a lot of rocks and send it to them.

This is very simple - just do not send the belt. The nice thing to do might be to call or to email, I have better luck with email. Tell them you've changed your mind and what would they like you to do with the label?
And may I state, I have been a customer, and a very good customer having lost a lot of my wardrobe. I have only one problem with them - the descriptions and photos are not always accurate. In fact about two thirds of the time the measurements are WAY off. The photos are greatly "enhanced", making a dingy white blouse, be it a Gucci, Prada, Chanel or whichever designer look sparkling white and in perfect condition. When a box arrives it is like being in Las Vegas - will it or will it not be a winner? Frequently, and obviously, there are more times my choices have been as expected or I would not be this happy customer. Just beware of the photos and measurements. Shop all sizes, "S", "M", and "L". When you see an item you might like then look first at the photo - how does it fit the model? What do the measurements say? I am what I guess is a "M", 5' 8" weighing 118. A US6 fits, generally depending on the designer. BUT I've bought {XS" to "XL". Go figure. They fit when they got here and if there was anything wrong, did not fit, did not look like pictured, etc, just return it. I NEVER buy an "On Sale" item as they can not be returned nor can a handbag be returned. Other than being on sale, marked "Not Returnable" or a handbag I have never found anything, in the clothing area, to not be returnable. I have found it is best to stay away from the low priced items, under $100. Unless they are marked "Excellent" or "Pristine". Generally items marked this way are good. It does distress me to read all of the really bad but uninformed comments written in these sections. I've NEVER had an item which was not made by the actual designer, as some state. I've just not had problems with TRR. If only those who are happy with the would state this. They MUST have a lot of happy customers considering the amount of business this new company does.
Sorry to have gone on and on about the other side of consigning. Hopefully my comment has helped you.

Just call or email them and say you changed your mind and won't be sending your belt. Why would you bother sending an empty box?

Are you certified to appraise jewelry