Can you apply for a student visa with a conditional offer?

Gov.uk says you "must have an unconditional offer" and a CAS (gov.uk). The pre-sessional exception in Appendix Student lets a university with a track record of compliance put both courses on one CAS if you are at B1 and it expects B2 by the end; see pre-sessional English.

Home Affairs says an application without a CoE "will be invalid", and a CoE is needed for every course in a package, with gaps under two calendar months (500 visa page). Packaging at least 10 or 20 weeks of ELICOS lowers the test score needed.

IRCC lets a DLI issue a conditional LOA for a prerequisite such as ESL. INZ says applicants outside New Zealand can apply with a conditional offer and get approval in principle, but need an unconditional offer before the visa is approved (INZ). Ireland's English rules allow a preparatory English course of up to 6 months with a study plan and fees paid for both courses.

In the US, a school issues an I-20 only after accepting you for a full course of study (8 CFR 214.3). Immigration rules change, sometimes at short notice. Confirm the current rule on the government page for your destination before you book a test or apply. This guide is general information, not legal or immigration advice.