Swisscom stock falls as the SMI exit reshapes trading

Published on 09/21/2026 at 13:48 | Editorial responsibility: Rafael Müller, Editor-in-Chief AD HOC NEWS

Swisscom stock closed at 652.00 euro on September 18, 2026, down 2.9 percent. The SIX move from the SMI to the SMIM takes effect on September 21, 2026.

Photorealistic mobile phone tower standing on an alpine meadow with snow-capped Swiss mountain peaks in the background under a dramatic orange and pink sunset sky — Swisscom AG (CH0008742519) – Mobilfunkmast in Schweizer Alpenlandschaft bei goldenem Sonnenuntergang über schroffen Bergspitzen, Illustration mit AI erstellt.

Swisscom stock (CH0008742519) closed at 652.00 euro on September 18, 2026, after a 2.9 percent drop from 671.50 euro. The shift from the SMI to the SMIM takes effect on September 21, 2026, and was highlighted by IT Boltwise as a likely trading catalyst.

Index rotation matters

The same report said the stock traded between 649.00 euro and 668.50 euro on September 18, 2026, with volume at 59,910 shares. It also noted that the SMI fell 0.8 percent to 13,786.72 points on that session, so Swisscom's slide did not happen in isolation.

For investors, the key point is the flow effect: passive funds and index products have to adjust to the new composition on the effective date. That can lift turnover even when the operating story is unchanged.

What the move means

Swisscom leaves the SMI and moves into the SMIM on September 21, 2026, with Galderma and Sandoz entering the top Swiss index. Index switches often change who trades the name and when, which can matter as much as the fundamental backdrop in the short run.

Stock near the lower band

Swisscom stock ended the latest completed session at 652.00 euro on the SIX, below the prior close of 671.50 euro and inside the 649.00 euro to 668.50 euro range reported for September 18, 2026. The move leaves the share price closer to the lower end of that band than to the upper edge.