Japan Net Worth Forecast: Salary, NISA, iDeCo, Pension, Retirement Pay and Mortgage, Year by Year

It steps one year at a time. Take-home pay comes from salary (with raises) less income tax, resident tax and social insurance, worked out separately for you and your spouse, and then living costs, one-off items and loan payments are subtracted. A surplus stays in cash (or is invested); in a year that falls short, saving is cut first, then cash, the taxable account (20.315% on the gain) and NISA are used, and anything still missing is treated as a loan. iDeCo and company DC money cannot be drawn before the payout age.

Each account grows as start balance × (1 + return) + the year's flows × (1 + return ÷ 2). Amounts are raised to each year's yen with the inflation figure and results are also shown in today's yen. The take-home part uses the same formulas as this site's take-home calculator and gives the same figures for 2026.

The larger basic deduction (¥1.04 million for total income up to ¥4.89 million in 2026-27) and the ¥740,000 minimum employment income deduction are special rules for 2026 and 2027. From 2028 the basic deduction is ¥990,000 for total income up to ¥1.32 million and ¥620,000 above that up to ¥23.5 million, and the minimum goes back to ¥690,000 (NTA, April 2026 leaflet). In the table above, income tax and resident tax together rise by ¥32,315 for someone paid ¥5 million.

The NTA says the basic deduction and the employment income deduction minimum from 2028 are to be reviewed every two years for consumer prices. With “Index tax amounts to inflation” ticked, deductions, brackets and the limits on insurance and contributions rise with prices, so if raises keep up with prices the tax burden does not change. Unticked, tax amounts stay at today's yen, so tax gets heavier just because nominal pay rises (Japan's actual brackets are not indexed).

The Special Reconstruction Income Tax falls to 1.1% from 2027 (running to 2047) and a Defense Special Income Tax of 1% starts (for the time being). The total stays at 2.1% through 2047; after that only the 1% defense tax is assumed to continue.

For employees without a company pension the monthly limit is ¥23,000 until November 2026 and ¥62,000 from December 2026. Employees with a company plan such as corporate DC can put in ¥20,000 a month, and no more than ¥55,000 together with the company plan, until November 2026; from December 2026 the separate ¥20,000 cap goes and the limit is ¥62,000 together with the company plan (for example, with a ¥30,000 employer contribution, up to ¥32,000 for iDeCo). The age to join also rises from under 65 to under 70 (Ministry of Health, Labour and Welfare).

Contributions are fully deductible from income for income tax and resident tax (social insurance does not fall). You choose when to take the money, from 60 to 75. Age 60 needs 10 or more years of participation before 60 (contributing or just holding); 8 years gives 61, 6 years 62, 4 years 63, 2 years 64, and less than that age 65. At 75 payment starts automatically (Defined Contribution Pension Act Arts. 33 and 34). The calculator warns you if the payout age you enter is earlier than that.

A lump sum is taxed as retirement income: half of (payment − retirement income deduction). The deduction is ¥400,000 × years of service (for iDeCo, the years you contributed) up to 20 years and ¥8 million + ¥700,000 × (years − 20) beyond that, with a floor of ¥800,000. In the same year the overlap of service periods is counted once against the total. In different years, if the retirement pay comes first the DC lump sum is adjusted when it falls within 19 years; if the DC lump sum comes first the retirement pay is adjusted when it falls within 9 years (from 2026 the window in that case grew from 4 to 9 years), and the later deduction loses the overlapping years.

In the example above (¥20 million retirement pay, ¥10 million DC), each is tax-free alone, but in the same year the income tax and resident tax are ¥993,262, with the DC lump sum 5 years after the retirement pay ¥962,842, and with the retirement pay 5 years after the DC lump sum ¥902,002. 20 years after the retirement pay it is ¥0 again. In the calculator you can change the payout ages, or take the DC money as an annuity (taxed as a public pension), and compare.

The basic pension is the FY2026 full amount of ¥847,300 a year times years of contributions ÷ 40. The earnings-related pension is average monthly pay (capped at ¥650,000) × 5.481/1000 × months covered. Past pay is assumed to equal today's pay, and future pay grows with your raise less inflation. Claiming early cuts 0.4% a month (24% at 60) and deferring adds 0.7% a month (84% at 75) (Japan Pension Service, Old-age pension guide, FY2026).

Not modelled: the pre-April-2003 formula, the per-bonus cap, supplements (the transitional addition, the spouse allowance), and the reduced pension for people who work while receiving it. Use the benefit level input to allow for future cuts. The pension grows with prices, is reduced by the public pension deduction for income tax and resident tax, and has the social insurance share you enter taken from it.

The installment quota is up to ¥1.2 million a year and the growth quota up to ¥2.4 million, with a lifetime limit of ¥18 million counted at book value, of which the growth quota can use ¥12 million, tested as in Article 37-14 of the Act on Special Measures Concerning Taxation (this year's purchases plus the previous year-end book value stay within the limit). Room freed by selling comes back from the next year, by the book value sold. Saving above the limits cannot be bought and is not invested. Gains inside NISA are not taxed. For the limits in more detail use the New NISA calculator.

Social insurance deducted from the pension (national health insurance, long-term care, late-stage elderly care) is entered as a share of the pension. For reference, in the Statistics Bureau's 2025 Family Income and Expenditure Survey retired couples aged 65+ paid ¥20,296 in social insurance on ¥228,614 of social security benefits (8.9%), and single people ¥5,912 on ¥120,212 (4.9%). Premiums between retiring and the start of the pension are not included. Put medical and care costs into living costs or add them as an item.

The housing loan tax credit (use the Japanese-only housing loan deduction calculator), deductions other than the basic deduction, social insurance and iDeCo contributions (spouse, dependants, life insurance, medical), the resident-tax adjustment credit (same as this site's take-home calculator), the one-year lag in resident tax, child allowances and school costs (add them as items), tax on savings interest and fund distributions, selling the home, future changes in premium rates, defined-benefit company plans, and several separate retirement payments. Tax uses the 2026-2027 rules and then the rules from 2028; later tax reform is not anticipated.