Under paragraph 32B of Appendix FM-SE, when a decision maker has:
(a) reasonable cause to doubt that an English language test in speaking and listening at a minimum of level A1 of CEFR relied on at any time to meet a requirement for limited leave to enter or remain in Part 8 or Appendix FM or Appendix Armed Forces was genuinely obtained; or
(b) information that the test certificate or result awarded to the applicant has been withdrawn by the test provider for any reason,
they may discount the document or result and the applicant must provide a new test certificate or result from an approved provider which shows that they meet the requirement if they are not exempt from it.
The Immigration Rules in Appendix FM-SE do not set out a timescale for when an applicant must provide a new test certificate or result where requested by the decision-maker, who should allow the applicant a reasonable amount of time to take another test.