You go to a speech therapist and get diagnosed with "Advanced Stutter" and/or "Speech block". (Then you apply via your countries social welfare system). Speech block is when some words are almost impossible to say, i.e "block" They will run some tests like ask you to read. Because speech also affects mental health you can additionally see psychiatrist to get diagnosed with MDD (Major Depressive Disorder). This will help but is not essential. The fact many stutterers that stutter severely is essentially speech disabled. You can't do any sales job. You can't even deliver pizzas because you must ring a buzzer to "Hello Mr this is your Pizza guy". (I personally struggle a lot with words starting in p,t,d and such.)