If he in service with govt or non govt hospital, his income will be treated as salary income. And if he is undertaking a profession, his income will be treated as PGBP income. ITR for Salary person ITR1 ITR for professionals ITR4
A Veteran if working in professional capacity i.e, running a practice of his own needs to file ITR4. If he is working as a salaried person in a hospital or clinic he needs to File ITR1