Settlement Checking Service (SCS)
Two year probationary period
If you have an entry clearance visa (issued abroad) the two year probationary period starts from the date your visa was stamped, by the Immigration Officer, when you entered the UK.
If you have a residence permit or a biometric residence permit the two year probationary period starts from when you were granted two years leave as a spouse or partner.
If you have previously had leave in another category, for example as a student, and switched to a spousal visa, you may be able to apply before the two years qualifying period. You must call the UK Border Agency to ask when you can apply if you come under this category.