Most places will putt the referral through at 22 but you won't be seen until 23 and if you live in Northern Ireland you have to be TTC for three years with no BFP, neither partner can have children, neither partner can be smoking and the woman has to have a BMI under 35 but they are bringing it down to 30. There are loads of other criteria they want as well. Lol.
I guess most of what I told you was unnecessary to you but I just kept typing. Lol. You know how it is. Lol.
Good luck. x