BRIDGES · Due Diligence and compliance

STR /SAR

Suspicious transaction report

STR/SAR — a suspicious transaction report that a bank is required to file with the regulator when there are signs of laundering or other risks.

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a dutythe bank’s
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  • 4 min read
  • Updated: July 2026
  • BRIDGES Research Team
In brief — 30 seconds
What it is
STR/SAR — a bank’s report of a suspicious transaction to the regulator
When
Where there are signs of money laundering or other financial risks
Who files
A bank or financial institution obliged by law
For the client
The filing is not usually disclosed
How to avoid it
Transparent and explainable transactions

In plain words

An STR/SAR (suspicious transaction report / suspicious activity report) is a report that a bank or financial institution is obliged to file with a special state body (the financial intelligence unit) if a transaction or a client’s behaviour raises suspicion of money laundering, terrorist financing or other breaches.

Filing such a report is not the bank’s decision to “punish” the client but its direct legal obligation: if it fails to file where there are clear signs, the bank itself is liable. The trigger may be an unusually large or atypical transaction, an unclear source of funds, splitting payments, or activity inconsistent with the client’s profile. An important detail: in many jurisdictions the bank is prohibited from telling the client that a report has been filed (the “tipping-off” rule).

For the client this means that their financial activity is constantly assessed for suspiciousness, and they may not even know that a report has been filed on a particular transaction. The only reliable protection is to conduct your affairs transparently: a clear source of funds, transactions consistent with your profile, readiness to explain any large transaction. We help clients structure their financial activity so that it gives no grounds for suspicion.

Where the risk of an STR/SAR arises

Large and atypical transactions
An unclear source of funds
Splitting payments
Activity inconsistent with the profile
International transfers
Ongoing account monitoring

What matters about STR/SARs

What it is
  • A report of suspicion
  • To the financial intelligence unit
  • The bank’s obligation
Triggers
  • Large transactions
  • An unclear source
  • Splitting payments
Distinctive feature
  • The client is not told
  • The tipping-off rule
  • Constant assessment
Protection
  • Transparent transactions
  • A clear source
  • Readiness to explain

How to reduce the risk

  1. 01A clear source of funds
  2. 02Transactions in line with the profile
  3. 03Documents for large transactions
  4. 04Readiness to explain
  5. 05No grounds for suspicion

What you need to know

  • STR/SAR — a bank’s report of a suspicious transaction to the regulator
  • Filing is the bank’s legal obligation, not a punishment
  • The triggers are large, atypical transactions and an unclear source
  • The client is not usually told a report has been filed
  • The protection is transparent and explainable transactions

Common mistakes

  • Carrying out transactions that do not fit your profile
  • Splitting large sums, arousing suspicion
  • Having no explanation of the source of funds
  • Assuming the bank is not obliged to report to the regulator
  • Changing the nature of your activity sharply without reason

What this means for a BRIDGES client

We help structure financial activity so that it does not arouse suspicion: a clear source of funds, transactions in line with the profile, documents for large transactions. That way the bank has no grounds for a report to the regulator, and your affairs are conducted transparently and calmly, with no hidden risks to the account.

Frequently asked questions

01 /What is an STR/SAR?

A report of a suspicious transaction or activity that a bank is obliged to file with the financial intelligence unit where there are signs of money laundering or other breaches.

02 /Is it a punishment for the client?

No, it is the bank’s legal obligation. If it fails to file where there are clear signs, the bank itself is liable. The decision is dictated by the rules, not by its attitude to the client.

03 /What can trigger a report?

An unusually large or atypical transaction, an unclear source of funds, splitting payments, or activity inconsistent with the client’s declared profile.

04 /Will I be told that a report was filed?

Usually not: in many jurisdictions the bank is prohibited from notifying the client that a report has been filed (the tipping-off rule). The client may not even know about it.

05 /How to reduce the risk?

Conduct your affairs transparently: a clear source of funds, transactions in line with your profile, readiness to explain large transactions with documents. We help set this up.

06 /Is it dangerous to split payments?

Yes, splitting large sums into small ones is a classic sign of suspicious activity. It is more likely to attract attention than hide the transaction. It is better to carry it out transparently.

See also

Read next

Klara Rihter
AuthorKlara RihterHead of Compliance and Due Diligence, BRIDGES
Dmitry Nagy
Reviewed byDmitry NagyInternational Tax Consultant, BRIDGES
Updated
July 2026
Version
1.0
Scheduled review
January 2027
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