A self-proving affidavit confirms that the required number of witnesses watched you sign your will. Your witnesses also must sign your will; after your death, the court will want corroboration that they did so in order to validate it. This would normally involve a court appearance where your witnesses would confirm under oath that you signed the will and establish that you appeared to be of sound mind at the time. However, most state courts accept an affidavit in lieu of such an appearance. This can save your loved ones a great bit of time and trouble if, at the time of your death, one or more of your witnesses are no longer living or can't be located.
Ideally, you'll create your affidavit at the same time you write your will. With everyone in place for the will signing, they can also put their signatures on this one extra document. An affidavit is not typically part of your will, but a separate document that you would attach to it. In some states – such as Montana – you can create your affidavit at a later date and have your witnesses sign it then, attesting that they were present when you signed your will and saw you do so.
What to Include
Your state might have statutory language – prescribed wording included in its legislative code – that determines what you must say in your affidavit for it to be legally recognized. Other states provide forms; you might be able to purchase one for your state from an online legal document provider. Short of that, you would typically begin by stating your name and identifying yourself as the testator – the person who wrote the will. You would explain that you're creating the affidavit to confirm that you signed your will in front of your witnesses, that you told them at the time that what you were signing was your will, and that they saw you do it. You might also add that you made the will voluntarily, without anyone coercing you, and that you’re of legal age to write the document. Your affidavit can have a separate section where your witnesses reiterate this same information, or you can create a separate affidavit for them to sign. Some states may require that each witness sign her own affidavit.
Typically, all signatures – yours and your witnesses – must be notarized on a self-proving affidavit. After all, the affidavit acts in place of your witnesses having to appear in court and testify under oath. The court requires confirmation that the people who signed the affidavit really were your will's witnesses, so they'll have to provide identification to a notary public, particularly if you create your affidavit at a later date.