JP freelancer this-year tax schedule (from prior return) — monthly cashflow
Builds a per-month calendar of this year's tax due dates and amounts (resident 4×, NHI 8×, business tax, income-tax prepay 2×, consumption mid-year) directly from your prior-year return (business income, taxable income, final income tax, consumption tax). Add this year's income, expenses, and fixed costs to see how much cash is left each month. Runs entirely in your browser.
How to use
Have your prior-year final return on hand (Form B + Blue Return ledger). Enter this year's monthly income, expenses, fixed outflows, payday, and current bank balance. These feed the remaining-cash calculation only; they do not affect tax. Enter your prior-year business income (sales − expenses), taxable income, final income tax, and consumption tax. Copy these from the prior-year return. Enter resident-tax flat portion and either auto-calc or manual NHI premium. Enable business tax if applicable and enter the category rate (%). Pick the simulation start (year / month). The simulation always ends in March of the following year. Click Run to see a per-month calendar with resident (×4), NHI (×8), business tax (×2), income-tax prepayments (×2), and consumption mid-year instalments laid out by due date. When a tax notice (payment slip) arrives, type the actual billed amount into the matching instalment field under ‘Override with actual billed amounts’. Blank fields keep the estimate; only the instalments you override are replaced in the calendar and totals.
In depth
前年確定申告書の数字が持つ機微性
このツールに入力する「前年の事業所得・課税所得・確定所得税額・消費税額」は、確定申告書の核心的な数字です。確定所得税額は年収から各種控除を引いた課税所得の大きさを推測する材料になり、消費税額は売上規模の下限を示します。これらを合算すると「この事業者の事業規模と税負担の実態」が浮かび上がります。
前年実績を入力するという性質上、このツールのデータは推測値ではなく確定値です。外部サービスに入力した場合、申告書レベルの精度で財務情報が外部に開示されることになります。
申告書データをアップロード型ツールに入力するリスク
税務申告書に記載された数字は、金融機関の融資審査でも使われる公式財務情報です。「確定所得税額 15 万円以上 = 予定納税対象」という情報は、この事業者が一定以上の所得を得ていることを示す客観的な指標です。こうした情報が外部サーバーに送信されれば、事業者のプロファイリングの精度を上げる素材になります。
確定申告書のデータを扱うツールこそ、ブラウザ外に出さない設計を選ぶ価値があります。
前年実績ベースの計算がブラウザ内で完結する仕組み
このツールは前年の確定所得税額（15 万円以上なら予定納税対象）・消費税額（48 万円超は中間納付 1 回、400 万円超は 3 回）・事業所得・国保料率を入力として、今年の納税スケジュールを JavaScript で構築します。東京都特別区令和 8 年度の国保統一料率を含むすべてのロジックがブラウザ内に実装されており、Network タブを開いた状態で操作してもリクエストは発生しません。
入力値は localStorage にローカル保存されるため、次回開いたときに復元されますが、データが外部に出ることはありません。実際に届いた通知書の実額で上書きする機能も、ページ内の状態管理のみで完結します。
通知書が届いたときの活用法
7 月に住民税通知書・予定納税通知書が届いたら、試算値と実額を比較してください。差額が大きい場合は、前年所得の入力値を見直すか、手動上書き機能で実額に置き換えてください。この操作で年間の納税合計が実態に近い値に更新され、残りの月の資金計画が立てやすくなります。
Income-tax prepayment thresholds and consumption-tax interim payment tiers
The income-tax prepayment (予定納税) is governed by Income Tax Act Article 104: if prior-year final income tax reached JPY 150k, one-third is due by July 31 and another third by November 30 (source: NTA Tax Answer No.2040). This tool auto-detects the threshold from the entered prior-year income-tax amount and removes the July/November entries from the schedule when below it. When current-year income is expected to drop substantially (disaster loss, business closure), filing a ‘prepayment reduction request’ (予定納税額の減額申請) with the tax office by July 15 can reduce or eliminate the obligation — this tool does not automate that request, so override the prepayment fields manually if planning a reduction.
Consumption-tax interim payments scale in tiers (Consumption Tax Act Article 42): no interim payment below JPY 480k of prior-year consumption tax; one payment (August, half the prior amount) for JPY 480k–4M; three payments (May, August, November, each one-quarter) for JPY 4M–48M; eleven monthly payments above JPY 48M. The tool selects the right tier from the entered prior-year consumption tax figure. Note: if the prior year was your first under the qualified-invoice regime (started October 2023), your consumption tax covers only part of the year and may fall below the JPY 480k threshold, removing interim payments from this year’s schedule.
The order tax notices arrive and how to use the override feature
Notices arrive in a consistent sequence: (1) mid-June: resident-tax assessment notice (special-collection or ordinary-collection variant); (2) late June: income-tax prepayment notice; (3) early-to-mid July: NHI tax notice; (4) early August: business-tax notice; (5) consumption-tax interim filing form (April for a March year-end, November for a September year-end). The override feature lets you replace each estimated figure with the notice amount as it arrives, progressively refining the annual total.
A practical workflow: (1) right after filing the prior-year return in March, enter the figures here to set the initial estimate; (2) override the resident-tax field when the June notice arrives; (3) override prepayment and NHI when those July notices arrive; (4) override the business-tax field in August; (5) read the refined total annual tax shown by the tool. Discrepancies over 10% between estimate and actual typically come from one of three causes: (a) a change in blue-return deduction tier eligibility, (b) crossing an NHI reduction threshold, or (c) a business-category reclassification for business tax. Identifying the root cause improves next year’s estimate as well. For a forward-looking calendar built from this year’s projected revenue and expenses, freelance-tax-calendar-jp covers that case; salaried workers with side income should use side-income-tax-jp — both stay browser-only.
FAQ
- How is this different from ‘freelance-tax-calendar-jp’?
- This tool uses your actual prior-year return to compute only this year's scheduled tax payments. Since resident, NHI, prepayments, and mid-year consumption are normally based on prior-year income, the numbers here are closer to what you will actually pay. Final filing (next March) is not computed.
- Is anything I enter uploaded?
- No. The simulator runs entirely in your browser and stores inputs in localStorage so they are restored next time.
- Where do I find prior-year final income tax?
- Form B line 45 ‘declared tax amount’. JPY 150k or above triggers this year's prepayments. The strict ‘prepayment baseline’ subtracts withholding, so confirm with the prepayment notice from the tax office for the exact amount.
- Does prior-year consumption tax include local consumption tax?
- Mid-year payment thresholds use the national portion only. Use the national portion of ‘consumption tax & local consumption tax total’ on the return. Over JPY 480k triggers one instalment; over JPY 4M triggers three.
- Which rates does NHI auto-calc use?
- Tokyo's unified FY2026 NHI premium rates. Switch to manual entry if your municipality differs.
- How do I skip business tax?
- Uncheck ‘Include business tax’. The rate input disappears and business tax is removed from the calendar and summary.
- Can I match the figures to my actual tax notices?
- Yes. After running the simulation, ‘Override with actual billed amounts’ shows a field for each scheduled instalment. Each placeholder shows the estimate; type the exact amount from the resident, NHI, business, prepayment, or consumption-tax notice into the matching instalment, and it replaces the estimate for that period. Fields you leave blank stay at the estimated value. The annual per-tax totals and the grand total are recomputed using the overridden amounts.
How to verify nothing is uploaded
This tool never sends your input outside your browser. The pages below explain how it works, how to audit it, and how the site is run.
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