Trading
Round Lots
Under Regulation NMS Rule 600(b)(93), TXSE assigns a round lot to every security primary-listed on the Exchange. Round lots are reset twice a year: March closing prices set the values effective the first business day of May, and September closing prices set the values effective the first business day of November. A round lot does not change between those dates, even after a stock split.
Round Lot File
One row per TXSE-listed security, with its new round lot, its previous round lot and the average closing price used. The file is not changed between cycles.
November 2026 Cycle
Effective Monday, 11/02/2026
Evaluation period: September 2026 · Published 10/21/2026, 2:45 PM ET
How Round Lots Are Assigned
TXSE averages each listing's closing prices over the evaluation month and matches the result to one of four tiers.
| Avg closing price | Round lot |
|---|---|
| $250.00 or less | 100 shares |
| $250.01 to $1,000.00 | 40 shares |
| $1,000.01 to $10,000.00 | 10 shares |
| $10,000.01 or more | 1 share |
How TXSE calculates the average:
- Closing prices are the official closes on the security's primary listing exchange.
- Only days with a close count, so a security that traded on fewer days is averaged over those days.
- For a security that transferred to TXSE during the evaluation month, closes from its previous listing exchange are used up to the transfer and TXSE closes after.
- For a security that transferred after the evaluation month, closes from its previous listing exchange are used.
- Closing prices are not adjusted for splits during the evaluation month.
- A new security that begins trading between evaluations, such as an IPO, receives 100 shares until its next evaluation.
File Specification
Comma-separated, with one header row and one row per TXSE listing. The file name carries the evaluation period (txse_round_lots_YYYYMM.csv). The last line is the time the file was generated, in UTC, followed by empty fields. Skip it when loading the file. Test symbols are not included.
| Field | Example | Description |
|---|---|---|
evaluation_period | 202609 | The year and month whose closing prices were averaged (YYYYMM). |
effective_date | 2026-11-02 | The first business day the round lot applies. |
symbol_id | 2792 | TXSE's identifier for the security. |
symbol | DDS, ET PRI | The TXSE symbol. A suffix is separated by a space. |
trading_days | 21 | The number of days in the evaluation month with an official closing price. |
average_closing_price | 648.06761904 | The mean of those closing prices, truncated (not rounded) to 8 decimal places. Blank when there were no closes. |
round_lot | 40 | The round lot size from the effective date. |
previous_round_lot | 40 | The round lot size before the effective date, so changes can be seen without comparing files. |
basis | evaluated | evaluated: the round lot comes from the average closing price. new_listing: the security had no closing prices in the evaluation month and receives 100 until its next evaluation. |
Round lot values are provided for informational purposes only.
Questions about round lots: marketops@txse.com