How to close checking account of deceased father?

Is this a minus figure. I think this is a 0 amount. I agree, just show them the death certificate. If an executor they should handle it. They will need to show a short certificate saying probate gave them permission to handle Dads affairs.

Have you asked the bank how to handle this?

Runaway, have you gone to a Chase branch and asked them specifically what they need to close the account?

Others have raised this issue, and it's important, and that is whether or not your father died intestate (without a will).  If so, heirs inherit what assets there are pursuant to FL statutes.

This should help determination successor rights if he did die intestate:
http://www.floridaprobatesolutions.com/florida/intestate/

If so, and if any of these relatives are available, they should go with you to Chase, as well as (already suggested) bringing a certified copy of the Death Certificate.   You should also bring ID for any intestate successors.   It wouldn't hurt to call a local Chase branch first to address what you'll need, and make an appointment.

You definitely need an Elder Law Attorney. I used one in Brandon, FL when I was caregiver for my Mom. Both before and after she passed. They are an excellent team and I will see if I still have their contact number and will post it for you.

In Nevada it depends on how much the estate is valued at. Here it needs to be more then $100K before it is required to go to court. Since the total of DW, Luz, was less than the required amount I only had to have the court clerk notarize a state form for me declaring myself the surviving spouse. This is a state form and no court appearance.
That form and the death certificate was all that was needed here. If your state or county has a web site your forms may be available on line.

The -99M or -99B is what Chase uses internally to designate that the account owner is deceased.

Google “Chase 99B debt Shelia Langan”.
Its a great article from 2018 on this.

go in person and show them the death certificate. That’s what we did for one of my MILs accounts and they closed it. If that won’t work and you executor of the estate, you may have to go to probate court and get paperwork.

If there is a will then the executor of that will will file probate and settle the estate's assets to the beneficiaries. If there is no will it comes down to getting someone in the family appointed to settle the estate. The account is a part of his estate with any properties, and etc. If there has been no stipulation made as to division of his assets then it works out some which way so much to spouse, so much to siblings, and whatever.
Basically I guess the short answer is that it is time to get a Lawyer to walk you through this.
Cali?
Some on the site do Estate management work, and might have some sort of answer to you that makes more sense.
Have they absolutely assured you that there is no POD (pay on death) listed on the account? Is there a will. Have you checked to looks for one, or were you told one exists?