What is a STOR?
Last reviewed 23 June 2026.
A STOR (Suspicious Transaction and Order Report) is a report filed with your national regulator under the EU Market Abuse Regulation (MAR) when a trade or order looks like it could be insider dealing or market manipulation. There's no firm-size exemption -- a one-person fund has the same obligation as a bank's trading desk.
Who has to file
Any person professionally arranging or executing transactions -- investment firms, fund managers, trading venues -- must file a STOR with the relevant national competent authority (in Estonia, Finantsinspektsioon) when they have reasonable suspicion that an order or transaction constitutes, or is an attempt at, insider dealing or market manipulation. "Reasonable suspicion" is a lower bar than proof: you don't need to be certain, you need to have a basis the regulator would consider reasonable.
What typically triggers a STOR
- Informed trading -- buying or selling shortly before a large, unexplained price move in the same direction as the trade
- Off-market execution -- a fill at a price detached from the day's trading range without an obvious justification (e.g. a block trade with disclosed terms)
- Unusual volume -- a single order or day's trading representing an outsized share of average daily volume, especially around news or price moves
- Layering or spoofing patterns -- orders placed and cancelled in a way that suggests an attempt to create a false impression of demand
What happens if you should have filed and didn't
Failing to file when reasonable suspicion existed is a breach in its own right under MAR -- separate from whatever the underlying trade turns out to be. That's why surveillance needs to run continuously on your own trades, not just be something you think about after a regulator asks.
Related
Do small AIFMs need to file STORs? · MAR compliance for small funds