The best place is probably in a safe deposit box because it will protect the documents from theft, fire, accidental loss, and most other types of damage or harm. A potential problem, though, is getting it opened after your death.
If you decide to keep your estate planning documents in a safe deposit box, consider naming a family member or your Executor or trustee as a joint holder on the box. That should simplify matters following your death because someone will be able to get into the box without delay. Also, if you live in a flood zone, be sure to put the document in a water-tight plastic bag. As many shocked clients have learned, water damage caused by flooding can ruin the contents of a safe deposit box.
Another place to keep your original estate planning documents is with the attorney who drafted them. However, I have decided not to retain original documents because of concern over theft, fire, flood, storms, or other loss of the document. It would also be prohibitively expensive to store hundreds or thousands of original documents. Also, what would happen if I were to die or my lawfirm were to cease operations?
Many people keep their original estate planning documents at home in a secure place. If you have a safe at home, that can be a good place to keep them. Be aware though, when thieves enter your home and discover a locked safe, they often take the whole safe thinking they'll find cash and jewelry. The last thing they want is a file containing your estate planning documents, but that's one of the things they'll get if you keep them in your safe. Therefore, unless your safe is bolted to the foundation of your house, it may not be the best place to keep your originals.
Another option with regard to a Will is to deposit it with the county clerk's office. Taking this approach can be a great idea, except that you need to be sure your records at home clearly indicate where the original can be found. Moving to a different county or changing your Will can cause problems as well.
More people than you would expect keep original Wills and other estate planning documents in an air-tight plastic bag at the bottom of their freezers. Freezers are well insulated and heavy, and have a way of withstanding fires, hurricanes, and tornadoes. Also, they don't die or move away, and they are stolen far less frequently than in-home safes.