Homemade In Transit auto window signs, papers, or stickers are not legal in Nebraska. You are stupid if you write "In Transit" on a piece of notebook paper and hang it in your recently purchased car window.
How do I obtain an “In Transit” sticker?
In Transit stickers can be issued by licensed dealerships only. They can only be issued once and are good for a 30 day period.
They cannot be used if the vehicle is purchased through a private sale. For vehicles purchased privately, you will need to carry your ownership papers with you until the vehicle is titled and registered in your name. You have 30 days from the date of purchase to title and register the vehicle.
source: Nebraska DMV Web Site FAQ
Where do we obtain "In Transit" stickers or signs?
Only dealers are authorized to provide "In Transit" signs. Nebraska dealers will provide them at purchase. If you purchased your car from other than a Nebraska dealer, keep the title, proof of insurance, and bill of sale with you when you are driving. You have 30 days to obtain plates from the date of purchase. In Transits cannot be renewed past the original 30 days. The State informs us that handmade "In Transits" are not legal even though you may see them on the street.
source: Sarpy County Nebraska DMV FAQ
2006 Nebraska Code - § 60-376 — Operation of vehicle without registration; In Transit sticker; records required; proof of ownership.
Subject to all the provisions of law relating to motor vehicles and trailers not inconsistent with this section, any motor vehicle dealer or trailer dealer who is regularly engaged within this state in the business of buying and selling motor vehicles and trailers, who regularly maintains within this state an established place of business, and who desires to effect delivery of any motor vehicle or trailer bought or sold by him or her from the point where purchased or sold to points within or outside this state may, solely for the purpose of such delivery by himself or herself, his or her agent, or a bona fide purchaser, operate such motor vehicle or tow such trailer on the highways of this state without charge or registration of such motor vehicle or trailer. A sticker shall be displayed on the front and rear windows or the rear side windows of such motor vehicle, except a motorcycle, and displayed on the front and rear of each such trailer. On the sticker shall be plainly printed in black letters the words In Transit. One In Transit sticker shall be displayed on a motorcycle, which sticker may be one-half the size required for other motor vehicles. Such stickers shall include a registration number, which registration number shall be different for each sticker or pair of stickers issued, and the contents of such sticker and the numbering system shall be as prescribed by the department. Each dealer issuing such stickers shall keep a record of the registration number of each sticker or pair of stickers on the invoice of such sale. Such sticker shall allow such owner to operate the motor vehicle or tow such trailer for a period of thirty days in order to effect proper registration of the new or used motor vehicle or trailer. When any person, firm, or corporation has had a motor vehicle or trailer previously registered and license plates assigned to such person, firm, or corporation, such owner may operate the motor vehicle or tow such trailer for a period of thirty days in order to effect transfer of plates to the new or used motor vehicle or trailer. Upon demand of proper authorities, there shall be presented by the person in charge of such motor vehicle or trailer, for examination, a duly executed bill of sale therefor, a certificate of title, or other satisfactory evidence of the right of possession by such person of such motor vehicle or trailer.
reference: Laws 2005, LB 274, § 76