From January 05, 2023, the £250 threshold amount specified in section 339A of the Proceeds of Crime Act has increased to £1,000. The threshold amount is the value of criminal property below which a bank or similar firm (a deposit-taking body, electronic money or payment institution) can carry out a transaction, in operating an account for a customer, without committing one of the main money laundering offences in sections 327 to 329 of POCA. Further guidance on the current threshold, and submitting better quality SARs more generally, can be found here.
https://www.nationalcrimeagency.gov.uk/who-we-are/publications/446-guidance-on-submitting-better-quality-sars-1/file