“Take my word for it.” In the world of patent law, this adage holds little weight. The first person to invent a useful, novel, and non-obvious idea is the legal inventor. That's why in cases of dispute, it's imperative to be able to prove the date when you first envisioned the invention. Regardless of what anyone tells you, mailing yourself a registered letter does not constitute legal proof of invention.

To protect your invention from potential challenges, the first thing you need to do is put your idea in writing. Your documentation must be complete, accurate and concise. Create research and development notebooks, and don't leave anything to guesswork. The notebooks should describe the invention in words and pictures, fully explaining how it operates. Your entries also must be sufficient to enable anyone with ordinary skill in the technology to understand the material. Include observations, calculations, sketches, photos and formulas if applicable. Also, write down any unusual or unexpected results, ideas or conversations, and date and witness them. Include receipts of your purchases and records of visits to attorneys.

The pages of your notebook should be consecutively numbered and permanently bound. Entries should be in pen. Never remove pages and don't skip pages. All entries, as well as the conclusion, must be dated. Never backdate your records; this may create some question about your truthfulness or accuracy. If you need to make a correction, date and initial it. Never erase. If you need to correct a portion, draw a line through it, leaving the underlying material legible. Use only one notebook per invention.

The notebooks should be witnessed weekly by two people you trust, but are not relatives, and who understand the significance of what they see and read. If you make a change to an original entry that has been witnessed already, the original witness should sign and date the change. The change also should be noted on the page corresponding to the date of the change. In addition, your witnesses should sign a non-disclosure agreement—a statement that binds them to respect the confidentiality of your work and allows you to discuss your invention with some protection. Also, you may want to consider getting the pages notarized by a notary public.

Legal proceedings can arise that might require a patent applicant to prove, before an administrative 
body or court, when he or she actually invented a particular invention. Such proceedings, for patent
 applications filed before March 16, 2013, are called "interference" proceedings, and for applications
filed since, they are called "derivation" proceedings. In either case, evidence of invention is crucial.

The Inventor Handbook is written as a preliminary guide for inventors and where legal rights are concerned, the reader should consult a qualified attorney.