The NH required my Mom to sign up for Medicaid but her Medicare and supplement were still in effect. Who pays?

The 3 payers will all take care of parts of the bill, which pays first I do not know for sure in your state. It doesn't matter if you "assigned" your mom's benefits to NH. The NH bill has to be paid, and they will bill Medicare first, anything not paid after Medicare goes to supplemental. If the supplemental denies and /or there is a part they don't cover, it goes to Medical Assistance. If there was a spend down in effect with M.A., the bill will be filed in probate against the estate. Social Security -- will do a debit against mom's account for the entire month of the month she died (they do not pro-rate it, unless things have changed recently ) so whatever you do, do not touch any of the Social Security monies from her last month--they will come after you!!! Best thing is to keep your hands off all her monies, until the estate is completely thru probate and all settled.

Good advice.

It depends on what state you are in.

Nursing home stays are a combination of services, all billed & paid differently.
You have the basic rent for the room, boarding, plus medical expenses.
Just like life before a nursing home, people have to pay for housing, food, and their doctor & Rx bills.

If your mother had a qualifying hospital stay prior to the NH, 100 days of rehab (in the nursing home building) is covered by Medicare. If there was no hospital stay, no days are covered by Medicare.

Generally it works like this - private money pays first (ss, pension, insurance), government pays last.

My mother's bills are paid in this order:

Medigap plans (like the AARP one) pay first for doctors & drugs.
Medicare pays next for doctors & drugs.
Medicaid pays last for doctors & drugs

Mom's income (social security, retirement, pension, etc.) pays first for NH rent/room/board. Whether you write the check, or it goes directly to the NH - doesn't matter.
Medicaid pays last for NH rent/room/board.

The state you are in may pursue what's called "recovery of fees" by going to your mom's estate and claiming cash & assets to try to pay back some of it.

This pay structure is to keep people from hiding money and expecting the government (which is all us taxpayers) to foot the bill. If there hadn't been so many people cheating the system, it would be a lot simpler. The 2005 Deficit Reduction Act changed the process to prevent people from hiding their wealth across the family as "gifts" and from hiding real property by changing the name on the deed at the last minute. The cheaters made it harder for everyone else.

If you are the executor of the estate, I strongly encourage you to get a probate lawyer to help you ASAP.

Medicare only pays full for rehab the first 20 days. After that I think its 50%. With what Medicare paid and Moms AARP supplement she paid 152. Medicaid was mentioned but Mom has some money so I didn't apply.