The Saudi Exchange spent the last session of the week changing what happens in the instant after an investor presses buy. From Sunday, a market order on the Main Market and Nomu will execute against available liquidity across as many as five price ticks, rather than at a single price level. Whatever remains unfilled at the fifth tick becomes a limit order at the last executed price. For most retail investors the difference will pass unnoticed. For anyone moving size through the book, it is the difference between an order that fills and an order that waits.
The exchange announced the change on Thursday and framed it as liquidity work. Chief executive Mohammed Al Rumaih called it an important step in improving efficiency and supporting the evolving needs of investors and market participants. The confirmed mechanics are narrow: more of a market order executes immediately, the price it can walk is capped at five ticks, and the residual converts rather than chasing. The design protects the order from its own urgency, which is what separates this from simply loosening price limits.
The timing is not accidental, and the context is visible in the exchange’s own nine-month tape. Argaam’s analysis of negotiated deals, the channel through which large blocks change hands off the open book, counted 2,063 transactions worth about SR23.6 billion on the Main Market between January and September, spread across 232 companies and a dozen listed REITs. Al Rajhi Bank led by value at SR2.98 billion, followed by Saudi National Bank and Rasan. Saudi Aramco was the most frequently negotiated name, with 88 deals. The top ten companies accounted for roughly half the total value.
Read together, the two facts describe one market with two circulatory systems. Size that cannot cross the open book without moving the price goes through negotiated deals, with their disclosure lags and bilateral pricing. Everything else queues on screen. A market-order mechanism that can absorb more volume at the moment of execution narrows the gap between the two, and every tick of depth the open book gains is a transaction that no longer needs the private channel. The five-tick change will not move SR23.6 billion back on screen. It signals which direction the exchange wants that traffic to flow.
The parallel markets tell the same story at different stages of maturity. Nomu recorded 103 negotiated deals worth SR792.7 million over the nine months, nearly two thirds of it a single May transaction in United Mining shares amounting to 63.2 percent of the company’s capital. The sukuk and bond board saw 57 negotiated deals worth close to SR7.8 billion, concentrated in government paper. A debt market whose secondary life runs through a few dozen block trades a year is a market still being assembled, and the exchange’s microstructure work applies there with more room to run.
The change also lands in a crowded month for market rulebooks. The Capital Market Authority has two consultations closing in late October, covering underwriting practice and margin access, with effective dates planned for November. Foreign investors hold 11.22 percent of the market excluding Aramco, a share that has climbed slowly and that every piece of this machinery is built, in part, to serve: institutions allocating to Riyadh measure a market by how much it costs to get in and out at size, not by its index level.
Sunday’s session carries a second debut alongside the mechanism: the first trading day after a week in which the index closed at 10,392.97. The test of the new behavior will not come on a quiet morning. It will come the first time a heavy order meets a thin book, and the fill prints across five levels instead of standing still. Watch the exchange’s follow-up notices, and watch whether the negotiated-deal share of turnover begins, slowly, to give ground.