確定申告が必要な条件につきましては下記（国税庁HPから引用）をご参照ください。
1. 給与を1か所から受けていて、かつ、その給与の全部が源泉徴収の対象となる場合において、各種の所得金額（給与所得、退職所得を除く。）の合計額が20万円を超える
2. 給与を2か所以上から受けていて、かつ、その給与の全部が源泉徴収の対象となる場合において、年末調整をされなかった給与の収入金額と、各種の所得金額（給与所得、退職所得を除く。）との合計額が20万円を超える※給与所得の収入金額の合計額から、所得控除の合計額（雑損控除、医療費控除、寄附金控除及び基礎控除を除く。）を差し引いた残りの金額が150万円以下で、さらに各種の所得金額（給与所得、退職所得を除く。）の合計額が20万円以下の方は、申告は不要です。
また、確定申告（副収入の場合）に関してはこちらの国税庁HPをご参照ください。（下記URL）
https://www.nta.go.jp/taxes/shiraberu/shinkoku/kakutei/kakutei/fukugyo.htm
Please refer to the following (quoted from the NTA website) for the conditions that require a final tax return.
1. If you receive salary from one place and all of the salary is subject to tax withholding, the total amount of various incomes (excluding salary income and retirement income) is 200,000 yen. Exceed
2. If you receive salary from two or more places and all of the salary is subject to tax withholding, the amount of salary that has not been adjusted at the end of the year and the amount of various income (salary income, retirement) Total amount with income exceeds 200,000 yen * Total amount of income deduction from total amount of salary income (excluding miscellaneous loss deduction, medical expenses deduction, donation deduction and basic deduction) If the remaining amount after deducting is less than 1.5 million yen and the total amount of various incomes (excluding salary income and retirement income) is 200,000 yen or less, no declaration is required.
For final tax returns (in the case of additional income), please refer to the NTA website here. (URL below)
https://www.nta.go.jp/taxes/shiraberu/shinkoku/kakutei/kakutei/fukugyo.htm