Upvote:5
The guidance says they should not be more than a year old. Ideally, you'll show several months of statements, so by definition most of them will be more than a month old.
See https://www.gov.uk/government/publications/visitor-visa-guide-to-supporting-documents:
Section 4: documents you should not send unless specifically requested
This page provides guidance on the types of documents that are not required to consider your application.
if you are applying as a family/group you do not need to provide multiple copies of the same documents
bank statements or letters issued more than 1 year before the date of application
...