Either Branch of an ETF's Market Price Can Be Set Without a Trade

An exchange-traded fund's page carries three figures for yesterday: a net asset value per share, a market price, and a premium or discount of, say, -0.09%. The third is built from the first two, the second is defined by a rule that offers a choice, and the choice leaves no mark on the output.

So the question is narrow. When a fund posts a premium, what sat on the price side of that subtraction? The trail runs from a Commission rule into an exchange rulebook and ends where no screen hints: on a quiet day that side can be an average of quotes ending five seconds before the bell, with no trade in it.

Two Readings of One Percentage

The output is defined tightly. Electronic Code of Federal Regulations, 17 CFR 270.6c-11 (Exchange-traded funds) paragraph (a)(1) says "Premium or discount" means "the positive or negative difference between the market price of an exchange-traded fund share at the time as of which the current net asset value is calculated and the exchange-traded fund's current net asset value per share, expressed as a percentage of the exchange-traded fund share's current net asset value per share."

Read the timestamp inside that sentence. Both legs are pinned to one instant, "the time as of which the current net asset value is calculated". It is not a close compared with a close, and the denominator is net asset value, not price.

Then the same paragraph defines the price leg once, in two branches. "Market price" means "The official closing price of an exchange-traded fund share; or" — second branch — "If it more accurately reflects the market value of an exchange-traded fund share at the time as of which the exchange-traded fund calculates current net asset value per share, the price that is the midpoint between the national best bid and national best offer as of that time."

The branches are not symmetric. The second carries the valuation instant in its own words and switches on through a judgment about accuracy; the first names a price the exchange produces and attaches no clock to it. Paragraph (c)(1)(ii) requires a fund to post each business day "The exchange-traded fund's current net asset value per share, market price, and premium or discount, each as of the end of the prior business day". That list names three figures; which branch built the middle one is settled by the definition.

The Net Asset Value Leg Runs on a Board's Clock

If both legs hang on the valuation instant, who sets it? Electronic Code of Federal Regulations, 17 CFR 270.22c-1 (Pricing of redeemable securities for distribution, redemption and repurchase) paragraph (b)(1) answers: "The current net asset value of any such security shall be computed no less frequently than once daily, Monday through Friday, at the specific time or times during the day that the board of directors of the investment company sets, in accordance with paragraph (d) of this section, except on:" and then three kinds of days.

The carve-outs are "(i) Days on which changes in the value of the investment company's portfolio securities will not materially affect the current net asset value of the investment company's redeemable securities;" then "(ii) Days during which no security is tendered for redemption and no order to purchase or sell such security is received by the investment company; or" then "(iii) Customary national business holidays described or listed in the prospectus and local and regional business holidays listed in the prospectus".

That paragraph names no clock time of its own. It names a frequency floor, a five-day week, a board, and three exceptions, with the prospectus holiday list forming part of the definition. So the phrase in Rule 6c-11, "the time as of which the exchange-traded fund calculates current net asset value per share", resolves through a board resolution.

The Official Closing Price Is Not One of the Rule's Defined Terms

Paragraph (a)(1) of Rule 6c-11 defines thirteen terms, in this order: Authorized participant, Basket, Business day, Cash balancing amount, Creation unit, Custom basket, Exchange-traded fund, Exchange-traded fund share, Foreign investment, Market price, National securities exchange, Portfolio holdings, Premium or discount. "Official closing price" is not among them; the phrase occurs there only inside the definition of "Market price". Branch one is a pointer at an exchange rulebook.

Nasdaq's answer sits in Equity 4, Rule 4754(b)(4), reproduced in Securities and Exchange Commission, Exhibit 5 to File No. SR-NASDAQ-2025-047 and in Nasdaq, Rule Filing SR-NASDAQ-2025-047 of June 24, 2025. The base sentence is plain: "The Nasdaq Closing Cross price will be the Nasdaq Official Closing Price for stocks that participate in the Nasdaq Closing Cross." The dissemination sentence adds two conditions: "Fifteen minutes after the close of trading, Nasdaq will disseminate via the network processor a trade message setting the Nasdaq Official Closing Price as the official Consolidated Last Sale Price in each Nasdaq-listed security in which one round lot or more is executed in the Nasdaq Closing Cross where the closing price differs from the Consolidated Last Sale Price."

Then the branch for a thin fund, which that 2025 filing extended from an absent closing cross to a closing cross trade under one round lot: "If a Nasdaq-listed security that is an exchange-traded product ("ETP" and as defined below in (vii) for purposes of this rule) does not have a closing cross, or if a closing cross trade is less than one round lot, then the time-weighted average midpoint ("T-WAM") of the NBBO will be used as the Nasdaq Official Closing Price with the following parameters:". The Federal Register, Notice of Filing and Immediate Effectiveness of Proposed Rule Change To Amend Equity 4, Rule 4754(b)(4) gives the aim, to "expand the use of T-WAM to one other scenario, specifically when there is less than one round lot executed in the Closing Cross", because "using the T-WAM of the NBBO would be more indicative of the actual value of the ETP". It also records that "both Arca and BZX currently have substantively identical processes".

The parameters were set six years earlier. Federal Register, Order Granting Accelerated Approval Relating to the Nasdaq Official Closing Price for Nasdaq-Listed Exchange-Traded Products (File No. SR-NASDAQ-2019-061) describes T-WAM as "a time-weighted average midpoint value calculation", measured across "3:58:00 p.m. to 3:59:55 p.m." and "based on quotes observed every second", with an eligible quote being "a quote whose spread is no greater than a value of 10% of the midpoint price". Two filters follow: "Quoted spreads within the T-WAM time period that are greater than 10% of the midpoint price would be excluded", and "Crossed NBBO markets would also be excluded from the T-WAM calculation." Nasdaq's own Nasdaq, Enhanced Closing Price for ETPs adds that the calculation "excludes the BBO quotes observed in the 5 seconds prior to the close 03:59:56pm - 4:00:00pm", and that "If there are no eligible quotes for the T-WAM, Nasdaq uses the consolidated last sale as the official closing price".

Count what that leaves. From 3:58:00 p.m. to 3:59:55 p.m. is 115 seconds, so one observation per second inclusive of both ends gives 116 marks, and the five seconds nearest the bell are discarded on purpose. For a fund whose closing cross trades 99 shares, the figure labeled "official closing price" is a filtered average of quoted midpoints that ends before the bell, and branch one turns it into the posted premium.

One Round Lot Decides Which Formula Runs

The switch between a cross price and a quote average is a share count, which makes the round lot definition load-bearing. It is not the flat hundred shares most people carry in their heads. Electronic Code of Federal Regulations, 17 CFR 242.600 (NMS security designation and definitions) paragraph (b)(93) has four subparagraphs, of which the first two carry the counts: "Round lot means: (i) For any NMS stock for which the average closing price on the primary listing exchange during the prior Evaluation Period was: (A) $250.00 or less per share, an order for the purchase or sale of an NMS stock of 100 shares; (B) $250.01 to $1,000.00 per share, an order for the purchase or sale of an NMS stock of 40 shares; (C) $1,000.01 to $10,000.00 per share, an order for the purchase or sale of an NMS stock of 10 shares; (D) $10,000.01 or more per share, an order for the purchase or sale of an NMS stock of 1 share; and (ii) New NMS stocks. Any security that becomes an NMS stock during an operative period as described in paragraph (b)(93)(iv) of this section shall be assigned a round lot of 100 shares."

Two consequences. The threshold that flips a closing price from an auction print to a quote average depends on a price band measured over a prior evaluation period, a property of the tape's history rather than of today's session. Subparagraph (iii) fixes that period as all trading days in March for the round lot assigned on the first business day of May, and all trading days in September for the round lot assigned on the first business day of November; subparagraph (iv) keeps each assignment operative from that May through the last business day of October, or from that November through the last business day of the following April. And a security that becomes an NMS stock during an operative period is assigned 100 shares whatever its price, so two funds at the same price can sit on opposite sides of the switch.

A share count below a round lot also decides which field a trade may touch, traced in An Odd Lot Prints, Adds to Volume, and Never Sets the Last Sale. Here the direction inverts: an odd lot in the cross does not merely fail to set the close, it replaces it with an average of quotes.

The Spread Figure Has Its Own Sampling Grid

One more number on the same page runs on a third clock. Rule 6c-11 paragraph (c)(1)(v) requires "The exchange-traded fund's median bid-ask spread, expressed as a percentage rounded to the nearest hundredth, computed by: (A) Identifying the exchange-traded fund's national best bid and national best offer as of the end of each 10 second interval during each trading day of the last 30 calendar days; (B) Dividing the difference between each such bid and offer by the midpoint of the national best bid and national best offer; and (C) Identifying the median of those values".

Three features matter to anyone reading that as a trading cost. It samples on a ten-second grid while the closing price above samples every second, so two published numbers describe one quote stream at different resolutions. It spans 30 calendar days, not a fixed count of sessions. And it reports a median, insensitive by design to the widest observations, the ones a market order is likeliest to meet on a bad afternoon. The rule text does not state the hours of a trading day here; across a six-and-a-half-hour session, 23,400 seconds give 2,340 intervals per day, but that is arithmetic on an assumption, not a number the rule prints.

Neighbouring items fix the history: (c)(1)(iii) requires a table of the days the shares traded at a premium or discount over the most recently completed calendar year and quarters since, (c)(1)(iv) a line graph across the same span. Paragraph (c)(1)(vi) sets the alarm: "If the exchange-traded fund's premium or discount is greater than 2% for more than seven consecutive trading days, a statement that the exchange-traded fund's premium or discount, as applicable, was greater than 2% and a discussion of the factors that are reasonably believed to have materially contributed to the premium or discount, which must be maintained on the website for at least one year thereafter." Securities and Exchange Commission, Exchange-Traded Funds: A Small Entity Compliance Guide renders the spread item as "Median bid-ask spread over the most recent thirty calendar days". Premiums built from quote averages trip that trigger exactly as auction prints would.

Concrete Framework

One, identify the price branch. Did the posted figure use an official closing price, or a midpoint of the national best bid and offer struck at the valuation time? A series that switches branches mid-history is two series.

Two, find the valuation time. Rule 22c-1(b)(1) sends you to a board resolution and the prospectus holiday list. Both legs hang on that timestamp, so a board striking value away from the equity close yields a premium comparing one moment's price with another moment's valuation.

Three, check the venue and the closing print. For a Nasdaq-listed product, did the closing cross trade one round lot or more? If not, the official closing price is a time-weighted average midpoint over 3:58:00 p.m. to 3:59:55 p.m., filtered for spreads wider than 10% of the midpoint and for crossed markets.

Four, keep the grids apart. A premium is one timestamp; a median bid-ask spread is a ten-second grid over 30 calendar days; a thin product's closing price is a one-second grid over 115 seconds. No arithmetic converts one into another.

What Would Invalidate This

If a fund elects the midpoint branch of "Market price" every business day, the exchange-rulebook chain is irrelevant to its disclosure and only the board's valuation time matters. The Nasdaq material would then describe a number that reaches the tape but not the fund page.

If a fund's round lot is not what paragraph (b)(93) implies for its current price — the prior Evaluation Period average sat in another band, or an operative period assigned the 100-share default — the threshold in check three moves, and a print that looked like an odd lot was a round lot.

If the T-WAM parameters have been amended since the 2019 approval and the 2025 expansion, the window, the 10% eligible-quote test or the excluded five seconds could differ. They come from the notices cited, not from the sentences of Rule 4754(b)(4) reproduced above, so they are the part likeliest to move while the quoted rule text looks unchanged.

And if Nasdaq's statement that "both Arca and BZX currently have substantively identical processes" is stale, premium histories are not comparable across venues. The Commission approved a formula for the other venue in 2018 under the heading "Order Approving a Proposed Rule Change To Amend NYSE Arca Rule 1.1(ll) To Modify the Formula for Establishing the Official Closing Price for a Derivative Securities Product When There Is No Closing Auction or if the Closing Auction Is Less Than One Round Lot, by Excluding the NBBO Midpoint if the Midpoint Multiplied by 10% Is Less Than the NBBO Spread or if the NBBO Is Crossed", which shows the same mechanism, and the same 10% test, reaching past Nasdaq. A heading is not a current rulebook, so read the live Arca text before any cross-venue claim.

None of this makes a posted premium wrong. It makes it a composite: a board-set valuation instant on one side, and on the other a price that may be an auction print, a filtered average of quoted midpoints, a consolidated last sale, or yesterday's number. The same silence surrounds any figure a rule points at instead of defining, traced in Reading the Reference Price and Percentage Parameter That Set a Limit State Band. A field can be honest about its value and mute about its construction.