Here is our alternative:
For those who need to use a 10 x 13 envelope, we suggest you use a plain 10 x 13 envelope (purchased from your local office supply store) and and then affix the label to the outside of the regular envelope.
The Label page: We would suggest purchasing a 8 1/2" x 11" label sheet (sticky labels) from your local office supply store. Most office supply stores have these in stock all the time. You would just print on the sticky label and then affix to the outside of the sealed envelope. Just be sure the green banner is visible on the top of the front and back of the letter/mail piece. You can also print the label page on plain paper and affix using tape or glue; just be sure the label is secure on all sides.
The Green Banner: USPS requires a green USPS Certified Mail banner to be visible on the top of the front and back of every piece of Certified Mail.
To get a label with the green banner, on Step 3 when you're choosing your Envelope type, choose
"Certified Mail: Plain Envelope: 9" x 12"Flat Size (prints green banner)."
Just remember to print your label in color.
If you don't have a color printer, choose the envelope type:
"Certified Mail: Plain Envelope: 9" x 12"Flat Size."
Just be SURE you have some of the PS Form 3800-n Certified Mail stickers from USPS to add to your envelope. You can order the PS Form 3800-n green Certified Mail stickers from USPS.com