The use of a bank safe deposit box is not recommended. One of the main reasons for this is due to the fact that these boxes are not always accessible since most banks are closed on nights, holidays, and weekends making it impossible to access your valuables or important documents when you need them or in the case of an emergency.

Consider alternatives, such as a home safe that is bolted to your floor, for storing these important items:

1. Cash – If you need cash in an emergency, the bank may not always be accessible. Due to inflation, cash also loses buying power over time. Instead, consider depositing your cash in an interest-bearing account or a certificate of deposit. Some banks may even forbid storing cash inside a safe deposit box, and keeping cash inside a safe deposit box makes it ineligible for FDIC insurance.

2. Passport – Although it is vital to keep your travel documents safe, keeping a passport inside a safe deposit box can be risky, especially in the case of emergencies. If you need to book a last-minute flight during hours when the bank is closed, your passport will be inaccessible.

3. Original Copy of Your Will – After your passing, your bank will seal access to your safety deposit box until an executor can prove they have the legal right to access it. This can delay the probate of your Will and impede your heirs from receiving their inheritances.

4. Letter of Instruction – A letter of instruction outlines your instructions for after your passing, such as burial wishes and specific bequests. Like your Will, if you store your letter of instruction inside a safe deposit box, once you are deceased, it will be sealed inside until an executor can prove their legal right of access. This could delay and even obstruct your final wishes from being implemented.

5. Durable Power of Attorney – A Durable Power of Attorney is a legal document that grants control of your legal and financial affairs to a trusted person if you become unable to handle them yourself. If you store your Power of Attorney inside a safe deposit box, then it may become inaccessible should you find yourself incapacitated, and the person entrusted with the Power of Attorney may find themselves incapable of carrying out their duties.

6. Advance Directives for Health Care – Two documents vital to your health and estate planning are your Living Will and Health Care Proxy. A Living Will states your wishes for end of life care, and a Health Care Proxy designates who will make medical decisions on your behalf if you are unable to do so yourself. If both documents are sealed away in a safe deposit box, your wishes may not be carried out.

7. Uninsured Jewelry and Collectibles – Although keeping precious items in a safe deposit box may seem like a good idea, you should only keep valuables in a safe deposit box if they are insured. Neither the FDIC nor the bank itself insures the contents of a safe deposit box unless otherwise stated. To prevent losses, it is best to get your valuables insured.

8. Spare Key – If you keep spare keys in your safe deposit box, you will only be able to access them during operating hours, and if you have the box’s key with you. If you attempt to access your spare key when the bank is closed, or if the key to your safe deposit box is locked away inside your house, you won’t be able to retrieve your spare keys.

9. Illegal or Dangerous Items – Refrain from keeping illegal items in your safe deposit box. Firearms, explosives, illicit drugs, and hazardous materials are typically prohibited. Be sure to check your bank's safe deposit box agreement regarding what is and what is not allowed in your box.

Source: https://www.kiplinger.com/slideshow/saving/t005-s001-things-you-ll-regret-storing-in-a-safe-deposit-box/index.html