Mini Index Options Explained: XSP, XND, MRUT

Mini index options are smaller versions of the standard cash-settled index contracts: the same index and the same settlement mechanics, at a fraction of the notional. They answer one specific problem, which is that a full-size S&P 500 contract controls more money than many accounts hold. The SPX against SPY question is a separate comparison and is settled in SPX vs SPY options; this page picks up underneath both of those instruments.

What are mini index options?

Four listed contracts make up the family in the US market. Each is written on an index that is a fixed fraction of a headline benchmark, and each settles in cash.

• XSP, the Mini-SPX Index option. The XSP index is one tenth of the S&P 500 level. The multiplier is $100, so one contract carries one tenth of the notional of an SPX contract.
• NANOS. Written on that same Mini-SPX index, with a multiplier of $1. One nano is one hundredth of an XSP contract, the smallest listed index option in the US.
• XND, the Nasdaq-100 Micro Index option. The XND index is one hundredth of the Nasdaq-100 level, with a $100 multiplier. The divisor and the multiplier cancel: one XND contract carries the Nasdaq-100 level itself, in dollars, one hundredth of an NDX contract.
• MRUT, the Mini-Russell 2000 Index option. The MRUT index is one tenth of the Russell 2000 level, with a $100 multiplier. One contract is one tenth of a RUT contract.

The pattern is not unique to US benchmarks. Japan's index complex is built the same way, with a large contract and a smaller sibling on the same underlying: see Nikkei 225 options explained.

What does one mini index contract control?

Notional is the sizing number: the index level multiplied by the contract multiplier, which is the dollar exposure one contract carries. The panel below tracks that figure for the three headline US benchmarks, using each one's tracking fund as the priceable stand-in, and shows how the number has drifted.

SELECT
    toString(toStartOfMonth(date))                                   AS month,
    formatDateTime(toStartOfMonth(date), '%b %Y')                    AS month_label,
    round(argMaxIf(toFloat64(close), date, ticker = 'SPY') / 10, 1)  AS sp500_usd_thousands,
    round(argMaxIf(toFloat64(close), date, ticker = 'QQQ') / 10, 1)  AS nasdaq100_usd_thousands,
    round(argMaxIf(toFloat64(close), date, ticker = 'IWM') / 10, 1)  AS russell_usd_thousands
FROM global_markets.stocks_daily_aggs
WHERE ticker IN ('SPY', 'QQQ', 'IWM')
  AND date >= today() - 1095
GROUP BY month, month_label
ORDER BY month

A standard option covers a lot of 100 fund shares. As of Sep 2026, that lot came to roughly $77.1 thousand on the S&P 500 fund and roughly $28.2 thousand on the Russell 2000 fund. At the start of the 37 month window, in Sep 2023, the S&P lot ran about $42.7 thousand.

Read those figures as stand-ins for the minis. The XSP index sits at one tenth of the S&P 500, and the fund tracks close to that same tenth, so one XSP contract carries approximately what the S&P lot above carries. MRUT lines up with the Russell 2000 fund the same way. A nano, at a $1 multiplier on the XSP index, carries about the price of a single fund share.

Three structural differences from options on SPY

1. Cash settlement. No shares change hands at expiration. An in-the-money contract pays a dollar difference.
2. European exercise. The contract can be exercised only at expiration, which rules out early assignment.
3. Section 1256 treatment. Broad-based index options sit in a different part of the US tax code from options on an ETF.

Cash settlement: what happens to an in-the-money contract

At expiration the exchange strikes one final settlement value for the index. Every in-the-money contract pays the difference between that value and the strike, multiplied by the contract multiplier, in cash. Nothing is delivered and no stock position appears in the account. Take a hypothetical XSP call struck at 640 against a final settlement value of 645: the payout is 5 index points times $100, which is $500 per contract, credited on the settlement date. An out-of-the-money contract expires at zero and disappears.

The equivalent on an ETF option is a delivery. An in-the-money SPY call turns into 100 long shares, with cash owed for them. What happens if an option expires in the money walks through both outcomes.

European exercise and the dividend timing it removes

American-style options on funds can be exercised by the holder on any session before expiration. That right shows up on the calendar in one specific place: a deep in-the-money call on a dividend-paying fund becomes a candidate for early exercise on the session before the ex-dividend date, when whoever holds the shares captures the upcoming distribution. A short call can be assigned that evening and open the next morning short 100 shares.

SELECT
    toString(ex_dividend_date)                      AS ex_date,
    formatDateTime(ex_dividend_date, '%b %e, %Y')   AS ex_date_label,
    round(toFloat64(max(cash_amount)), 4)           AS cash_amount_usd
FROM global_markets.stocks_dividends
WHERE ticker = 'SPY'
  AND ex_dividend_date >= today() - 1150
  AND ex_dividend_date <= today()
GROUP BY ex_dividend_date
ORDER BY ex_dividend_date

SPY has gone ex-dividend 13 times over the window above, most recently on Sep 18, 2026 at $1.8888 per share. Each of those dates is a scheduling event for anyone short an in-the-money SPY call. Mini index options carry none of it. European exercise keeps the position untouchable until expiration, and cash settlement leaves no shares to deliver. An index pays no dividend of its own.

Section 1256 and the 60/40 split

Broad-based index options, XSP and MRUT among them, are Section 1256 contracts under the US tax code. Open positions are marked to market at year end, and the gain is split 60 percent long-term and 40 percent short-term whatever the holding period was. Options on SPY, a fund rather than an index, follow the ordinary holding-period rules. The mechanics live in why index options are taxed 60/40. That is a description of a tax rule and not tax advice; a specific account belongs with a tax professional.

The honest trade-off: the minis trade thin

The size advantage arrives with a cost the marketing rarely mentions. XSP is the most active of the four and still turns over a small fraction of what SPX and SPY do. XND, MRUT and the nano tier are thinner again. Thin markets show up as a wider gap between the bid and the offer, and that gap is paid on the way in and again on the way out.

Work it through on hypothetical numbers. A contract quoted 2.00 bid at 2.05 offered has a five cent market: buying at the offer and later selling at the bid gives up $5 per contract at a $100 multiplier. The same contract quoted 1.85 bid at 2.15 offered has a thirty cent market, worth $30 on the identical round trip. The width does not shrink when the notional does, so on a contract carrying one tenth the exposure, that $30 is ten times the drag per dollar of exposure it would be on the full-size version.

Before assuming a fill, check the open interest on the exact strike and expiration, and read the posted bid and offer rather than the last trade. Open interest on a far-dated or far-out-of-the-money mini strike can be a handful of contracts. A listed market is not the same thing as a liquid one. The nano tier has drawn the thinnest participation of the four, so confirm with a broker that the series is listed and quoted before building anything around it.

When is the final settlement value struck?

Two conventions exist. The traditional third-Friday index series settles in the morning, from the opening prints of the index components on expiration Friday, which makes the Thursday before the last session in which the position can be closed. The weekly and end-of-month series settle in the afternoon, from closing prints on the expiration date itself. AM vs PM settled options covers the split, and the contract specification for the exact series is the document to read before holding into expiration.

The distance between the two conventions is measurable. It is the move between the morning print and the closing print on the same session.

WITH expiry_sessions AS
(
    SELECT
        date,
        abs(100 * (toFloat64(close) / toFloat64(open) - 1)) AS move_pct
    FROM global_markets.stocks_daily_aggs
    WHERE ticker = 'SPY'
      AND date >= '2015-01-01'
      AND date <  today()
      AND toDayOfWeek(date) = 5
      AND toDayOfMonth(date) BETWEEN 15 AND 21
      AND toFloat64(open) > 0
)
SELECT
    multiIf(
        move_pct < 0.25, 'under 0.25%',
        move_pct < 0.50, '0.25% to 0.50%',
        move_pct < 1.00, '0.50% to 1%',
        move_pct < 2.00, '1% to 2%',
                         'over 2%')  AS move_bucket,
    count()                          AS expiration_fridays,
    round(max(move_pct), 2)          AS bucket_high_pct
FROM expiry_sessions
GROUP BY move_bucket
ORDER BY min(move_pct)

The narrowest band, under 0.25%, holds 45 of those sessions. The widest band in the panel, over 2%, holds 3, with the largest single gap in it at 5.66 percent. The shape is a broad cluster of quiet expirations alongside a small tail. On the tail sessions, a morning settlement and an afternoon settlement would have produced very different numbers for the same strike.

FAQ

What is the difference between XSP and SPX options?

XSP is written on an index that is one tenth of the S&P 500 level, with the same $100 multiplier, so one XSP contract carries one tenth of the notional of one SPX contract. Both are cash-settled European-style contracts under Section 1256. The size differs, and the quoted market on XSP is generally wider.

Can mini index options be assigned early?

No. XSP, NANOS, XND and MRUT are European-style, so exercise happens only at expiration. There is no early assignment and there are no shares to assign, which is what removes the ex-dividend timing problem that American-style options on funds carry.

Are mini index options taxed the same as SPY options?

No. Broad-based index options are Section 1256 contracts, marked to market at year end with gains split 60/40 between long-term and short-term. Options on SPY follow the ordinary holding-period rules. Details sit in the 60/40 post linked above, and a specific situation belongs with a tax professional.

What happens if a mini index option expires in the money?

It pays cash. The exchange strikes one final settlement value for the index, and the contract pays the difference between that value and the strike, times the multiplier. No shares are delivered and no stock position appears in the account.

Are mini index options liquid enough to trade?

That varies by series and by strike, and it is checkable in advance. Look at the open interest and the posted bid and offer on the exact contract rather than the last trade. The minis quote wider than SPX or SPY, and on far-dated or far-out-of-the-money strikes the market can be very wide.

Every panel above ships with the SQL that produced it, expandable underneath the chart. To run the same measurements over a different benchmark or a longer stretch of history, ask the question in plain English on the Strasmore terminal.