Review your original will. Write down the exact provision you are changing using the codicil. Note the location of the provision in your will, such as "Article 4" or "Line 3."
Write your new provision down. Refer to the original provision's location and state in detail what is being changed.
Type your codicil. Use the same header for your codicil as you used in your original will. Include a sentence that references your original will by the exact date of the document. Insert your new provision. State all other provisions in the will are not being changed or modified and the document is not being revoked in its entirety by the codicil.
Sign and date your codicil. Your codicil must be dated so the court is aware the document was made after your will. Have your codicil signed by witnesses if you are required to do so under state law.
Put your codicil with your original will or file the document in probate court. Keep a copy of the codicil for your records.