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Hong KongDealing in securities on SEHK: sessions, matching and settlement
Securities on SEHK trade through a pre-opening auction, continuous morning and afternoon sessions, and a closing auction. Continuous trading matches on price then time priority. Trades settle on a T+2 cycle through CCASS with HKSCC as central counterparty. Short selling is permitted only in designated securities, covered and flagged.
The machinery of a securities trade is the most testable material on Paper 1, because every step of it is a fact with no shading. An order is either priced on the spread table or it is not. A short sale is either covered or it is naked. There is no reasonableness standard anywhere in this heading, and that should make it your favourite.
- Market
- The Stock Exchange of Hong Kong (SEHK), part of the HKEX group
- Matching
- Price then time priority in continuous trading; auction pricing at the open and close
- Trading unit
- Board lots set by the issuer; smaller quantities are odd lots
- Clearing
- CCASS, operated by HKSCC, acting as central counterparty
- Settlement cycle
- T+2
What are the SEHK trading sessions?
Four phases, in order: a pre-opening session, continuous trading in the morning, continuous trading in the afternoon, and a closing auction session.
The pre-opening and closing phases are auctions. Orders accumulate, no matching happens as they arrive, and a single price is then calculated to maximise the volume that can execute. Everyone who trades in that auction trades at that one price. Continuous trading works differently: each incoming order is matched immediately against the book if it can be.
Check current session times on the HKEX website rather than from a study note. They have changed before and they will change again.
How are orders matched?
Price first. Time second. A buy order at a higher price ranks ahead of every buy order at a lower price, regardless of when either was entered. Only when two orders share a price does entry time decide, and then the earlier one executes first.
That is the whole rule. It explains why traders improve their price to jump the queue, why a large resting order does not block better-priced flow, and why partial fills work the way they do.
What are board lots, odd lots and the spread table?
| Concept | What it means | Practical consequence |
|---|---|---|
| Board lot | The standard trading unit for a stock, fixed by the issuer | Orders in the main market are in multiples of the board lot |
| Odd lot | A quantity smaller than one board lot | Trades in a separate, thinner mechanism, usually at a worse price |
| Spread table | The minimum price increment, which widens as the price rises | An order priced off the table is invalid |
| Nominal price | The last traded price, used as a reference | Some order and price controls are set relative to it |
A shareholder left with an odd lot after a corporate action cannot expect the board-lot price. That single fact appears in questions more often than the rest of this section combined.
How does clearing and settlement work?
Securities trades clear through CCASS, the Central Clearing and Settlement System operated by Hong Kong Securities Clearing Company. Settlement runs on a T+2 cycle: the trade happens on day one, and the exchange of securities and money completes two business days later.
HKSCC acts as central counterparty. It interposes itself between the buyer and the seller, becoming the buyer to every seller and the seller to every buyer, so that neither participant carries the other's credit risk. If one side defaults, HKSCC deals with it rather than the innocent counterparty.
CCASS and HKSCC for SEHK securities. SEOCH for stock options traded on SEHK. HKCC for futures and options traded on HKFE. Swapping these is a standard distractor, and the fix is thirty seconds of memorisation.
What are the short selling rules?
- Designated securities only. The Exchange publishes the list, and a stock not on it cannot be short sold.
- Covered sales only. The seller must have a presently exercisable and unconditional right to vest the securities in the purchaser, normally via a stock borrowing arrangement.
- Flag the order. A short selling order must be marked as such when it is entered.
- Respect the tick rule. The sale may not be made below the best current ask price.
- Report large positions. Short positions above prescribed levels are reported to the SFC, which publishes aggregated data.
Naked short selling, meaning selling without that right to vest, is an offence under the Securities and Futures Ordinance rather than a rule breach handled by the Exchange. The Ordinance's business conduct provisions are where that prohibition sits; read the current text on e-Legislation for the wording. Candidates who treat it as a mere exchange matter answer the consequence questions wrongly.
A worked question
A client instructs a broker to sell shares she does not own, intending to buy them back later the same day. She has not borrowed the stock and has no arrangement to obtain it. What is the position?
- Permitted, provided the order is flagged as a short sale
- Permitted, provided the stock is a designated security
- Prohibited, because the sale is not covered, and naked short selling is an offence under the Ordinance
- Permitted, provided the shares are bought back before the close
What deserves your revision time here?
The priority rule, the settlement cycle, the clearing house mapping and the five short selling conditions. Everything else in this heading is context. If you can state those four things cold, you have covered what the paper reliably asks and you can stop.
Where I would soften the usual advice: candidates from a back-office or settlement background sometimes over-study this material because it is familiar and comfortable, then arrive at the topics that actually hurt with a week left. Comfort is not the same as coverage. Test the boundary with practice questions rather than another read-through.
Common questions
What are the trading sessions on SEHK?
A pre-opening auction session, continuous trading in the morning, continuous trading in the afternoon, and a closing auction session. The auctions calculate a single price that maximises executable volume; continuous trading matches orders as they arrive.
How are orders matched on SEHK?
By price then time priority. A better-priced order executes ahead of a worse-priced one whenever it was entered, and time only decides between orders at the same price, where the earlier order goes first.
What is CCASS?
The Central Clearing and Settlement System, operated by Hong Kong Securities Clearing Company. Securities trades clear through it on a T+2 cycle, with HKSCC acting as central counterparty so that neither participant carries the other's credit risk.
What is an odd lot?
A quantity of shares smaller than one board lot. Odd lots trade in a separate and less liquid mechanism, usually at a worse price than the board-lot market, which is why shareholders left with odd lots after corporate actions often lose value on exit.
Can you short sell any Hong Kong stock?
No. Only designated securities published by the Exchange may be short sold, the sale must be covered by a presently exercisable and unconditional right to vest the securities, the order must be flagged, the tick rule applies, and large short positions must be reported to the SFC.