Congratulations, you have the offer! Now comes the bureaucracy. Visa processes differ wildly depending on whether the host country views you as a "Student" or an "Employee."
1. USA: The F-1 Visa
Most PhD students enter on an F-1 visa.
- Key Document: I-20 Form (issued by the university).
- The Interview: You must prove "Non-Immigrant Intent." You need to convince the officer you plan to return home after graduation, even if you secretly hope to work in Silicon Valley.
- STEM OPT: Remember, a PhD in STEM allows you to work in the US for 3 years after graduation without an H1B visa.
2. UK: The Student Route (formerly Tier 4)
- Key Document: CAS (Confirmation of Acceptance for Studies).
- The Hidden Cost: IHS (Immigration Health Surcharge). As of 2025, you must pay for the NHS upfront. For a 4-year PhD, this can cost over £3,000 before you even arrive.
- Work Rights: Limited to 20 hours/week during term time.
3. Europe (Schengen Area): Student vs. Researcher
In countries like the Netherlands, Germany, or Switzerland, PhDs are often treated as employees, not students.
- Residence Permit: You might get a "Scientific Researcher" visa rather than a student visa.
- Benefits: This often counts towards permanent residency (PR) immediately, unlike student years in the UK or US.
Critical Check: Proof of Funding
For all visas, you must prove you can afford to live there.
- Self-Funded? You need liquid cash in a bank account for 28+ days.
- Full Scholarship? Your offer letter acts as your proof of funds. Ensure the letter explicitly states the monthly stipend amount.