Under Original Medicare, Part A can help pay for a skilled nursing facility (SNF) stay after a qualifying inpatient hospital stay—inside the same benefit period framework that governs hospital deductibles. Inside each benefit period, Medicare commonly describes up to 100 days of SNF coverage with day-band coinsurance (amounts published by CMS each year). Benefit-period orientation: Medicare Part A benefit period basics. Why observation status can block the SNF path: Observation status vs inpatient basics. Bill habits: Medical bills and insurance.
This page is the SNF day clock and coinsurance bands—not a full hospital benefit-period tour and not long-term custodial nursing-home coverage (which Medicare generally does not treat like skilled care).
Benefit period, qualifying stay, and the 100-day pool
| Rule of thumb | What it usually means | Watch-out |
|---|---|---|
| Benefit period | Begins with inpatient hospital or SNF admission; ends after 60 consecutive days without inpatient hospital / SNF care | A new period can mean a new Part A deductible |
| Qualifying hospital stay | Traditionally a 3-day inpatient hospital stay before SNF (observation days often do not count) | Confirm inpatient vs observation at the hospital |
| SNF days 1–20 (illustrative band) | Often $0 patient coinsurance for covered skilled days after deductible rules are met | Deductible may already have been owed for the benefit period |
| SNF days 21–100 (illustrative band) | Daily coinsurance (CMS sets the dollar amount yearly) | Medigap letters often target this band (What is Medigap) |
| After day 100 in that period | Patient-pay for continued SNF in that benefit period unless other coverage applies | A new benefit period requires the 60-day break rules |
CMS publishes Part A deductible and SNF coinsurance dollar amounts each calendar year—use Medicare.gov or your Medicare Summary Notice for the figures that apply to your year. Skilled care must meet Medicare’s skilled criteria (nursing or therapy on a daily basis under a plan of care)—not room-and-board custodial care alone.
How Medigap and Advantage change the bill
Standardized Medigap letters often help with SNF coinsurance per their outlines. Shop letters during open enrollment or guaranteed-issue windows when you qualify. Medigap premiums (UnitedHealthcare, Humana, Mutual of Omaha, regional Blues, etc.) are separate from the daily SNF coinsurance itself.
Medicare Advantage plans use plan SNF copays, prior auth, and network SNFs plus MOOP—not the Original Medicare 100-day table blindly (Medicare Advantage MOOP basics). Read the Evidence of Coverage.
Worked example: 28 SNF days in one benefit period
Avery has Original Medicare, no Medigap yet. Avery had a 4-day inpatient hospital stay (not observation), then transferred to a skilled nursing facility for rehab. Illustrative CMS figures for Avery’s year: Part A deductible already met in this benefit period; SNF coinsurance $209.50/day for days 21–100 (placeholder—use the official figure).
| SNF days used | Illustrative patient coinsurance |
|---|---|
| Days 1–20 | $0/day under standard Original Medicare SNF banding (after benefit-period deductible rules) |
| Days 21–28 (8 days) | 8 × $209.50 ≈ $1,676 |
If Avery leaves SNF on day 28, goes home for 70 days, then needs SNF again after a new qualifying inpatient stay, a new benefit period can restart deductible and day-count clocks. If Avery instead returns after only 20 days home, the stay may still sit in the same benefit period—day counts and coinsurance continue where they left off. Always trust the MSN and SNF billing office over a blog table.
Practical habits
- Ask “inpatient or observation?” before you assume SNF eligibility.
- Track SNF days used inside the current benefit period (1–20 vs 21–100).
- Look up this year’s official SNF coinsurance on Medicare.gov.
- Compare Medigap outlines specifically for SNF coinsurance—or confirm you have none.
- If on Advantage, use that plan’s SNF cost-sharing and prior-auth rules.
- Save MSNs until day counts and coinsurance match your calendar.
Checklist
- Confirm Original Medicare (A + B) vs Advantage before applying the 100-day table.
- Verify a qualifying inpatient hospital stay (observation often does not count).
- Budget for daily coinsurance if a stay may cross day 20.
- Read your Medigap outline for SNF gap coverage—or confirm you have none.
- Note whether a later stay starts a new benefit period (60-day rule).
- Re-shop supplemental coverage only with current letter charts and SHIP help.
Hospital lifetime reserve days are a separate pool from SNF day bands: Medicare lifetime reserve days basics. Home health uses 30-day periods and recertification—not the SNF 100-day table: Home health episode of care basics.
Hospice election periods (90-day then 60-day) are a separate clock from SNF days: Hospice election period basics.
SNF copay math for days 1–20 vs 21–100 and Medigap help: Medicare skilled nursing copay basics.
Educational only. Not insurance, tax, legal, or medical advice. Not a plan recommendation. Part A SNF day bands, coinsurance amounts, qualifying-stay rules, Medigap letter benefits, and Advantage designs change; confirm with Medicare.gov, your state SHIP program, the SNF, and insurer outlines of coverage.