My son, age 24, is living and working in Tokyo with a work visa for 3 years beginning in January of 2023. He works for a company that has divisions in the US. Before he left for Tokyo last January, he worked briefly for their division in Indiana where he made $2115. The rest of his income for 2023 was made in Tokyo. Is he required to file taxes in the US & Indiana (where he lived before going to Japan)?