Japanese Inheritance Tax 20% Surcharge Simulator | How Much More Do Non-Spouse/Child Heirs Pay?
Enter the total estate value, the composition of statutory heirs, the relationship of the person receiving the assets, and their acquisition ratio to estimate whether the 20% surcharge under Article 18 of the Japanese Inheritance Tax Act applies, and the resulting tax payable.
When someone other than the decedent's spouse or first-degree blood relatives (children, including grandchildren who become substitute heirs) acquires property through inheritance or bequest, a 20% surcharge is added to that person's inheritance tax under Article 18 of the Japanese Inheritance Tax Act. It exists to adjust the tax burden when property passes to someone outside the immediate family.
Whether the 20% Surcharge Applies, by Relationship
| Relationship of the person acquiring the assets | Subject to the 20% surcharge |
|---|---|
| Spouse | Not subject |
| Child | Not subject |
| Grandchild who is a substitute heir | Not subject |
| Adopted grandchild (not a substitute heir) | Subject |
| Sibling | Subject |
| Other beneficiary (niece/nephew, unmarried partner, third party, etc.) | Subject |
If a grandchild is legally adopted by the decedent, the adopted grandchild would normally count as a first-degree blood relative. However, under the proviso in Article 18, Paragraph 2, an adopted grandchild who is not a substitute heir (i.e., whose parent is still alive) is an exception and remains subject to the 20% surcharge. Please confirm the exact requirements with a tax accountant or tax office.
Run a Simulation from the Estate, Heir Composition, and the Recipient's Relationship
The twenty per cent inheritance tax surcharge
Where property passes by inheritance or bequest to someone other than the deceased's spouse or a relative of the first degree — a child, or a grandchild who has stepped into a deceased parent's place — that person's inheritance tax is increased by twenty per cent under Article 18 of the Inheritance Tax Act. Siblings, nephews and nieces, friends and corporations all fall within it. The provision exists to adjust the burden where property goes to someone distantly related, or to someone who is not an heir at all.
The point most often misjudged is the adopted grandchild. An adopted child is ordinarily a relative of the first degree, yet where a grandchild who is not standing in a deceased parent's place is adopted, the surcharge applies as an exception under the proviso to Article 18(2). The rule exists to close off the saving available by adopting a grandchild, skipping a generation and removing one occasion of taxation. Enter the estate total, the composition of the heirs, the recipient's relationship and their share, and this tool determines whether the surcharge applies and estimates the tax after it.
Sources used in this calculation
Statutory figures such as tax and insurance rates come from the public bodies listed below. They change when the law is revised, so please also check the primary source before relying on the result for an important decision.
- 20% surcharge on inheritance tax (who it applies to and the rate) — National Tax Agency (国税庁) Effective from 2003-04 ／ Last checked 2026-09-18
- Japanese inheritance tax rate table and basic exemption amount — National Tax Agency (国税庁) Effective from 2015-01 ／ Last checked 2026-09-17
How to estimate the tax after the surcharge
- Enter the total value of the estate The combined taxable value.
- Enter the composition of the statutory heirs Specify whether there is a spouse and how many children. The basic deduction follows from this.
- Choose the recipient's relationship For an adopted grandchild, the answer turns on whether they stand in a deceased parent's place. Choose the option that applies.
- Enter the share acquired Enter directly what percentage of the estate that person takes. A share other than the statutory one is perfectly acceptable.
- Read the ruling and the tax You see whether the surcharge applies and the tax before and after it.
Tips for getting more out of it
- The 20% surcharge is added on top of the calculated tax, unlike credits that are subtracted from it. Credits such as the surviving spouse's tax reduction are applied after the 20% surcharge.
- Siblings only become statutory heirs when the decedent has no children (or their substitute heirs) and no surviving parents, but a will can leave property to third parties beyond siblings as well, so the surcharge can apply to a wide range of recipients beyond the statutory heirs.
- Adopting a grandchild is sometimes used as a way to increase the basic deduction, but unless that grandchild is a substitute heir, they remain subject to the 20% surcharge — a heavier burden than adopting a child directly.
- The tax exemption for life insurance proceeds only applies when a statutory heir receives the payout, so it is worth checking that the exemption may not apply at all to a recipient who is subject to the 20% surcharge.
Where this helps
Deciding who to leave property to in a will
Confirm in money that a bequest to a sibling, nephew or niece carries a fifth more tax.
Testing the saving from adopting a grandchild
It removes an occasion of taxation but attracts the surcharge, so whether it comes out ahead cannot be known without calculating.
Considering a bequest to a non-heir
Establish in advance the tax burden of leaving property to a friend or a corporation.
Organising matters before seeing an accountant
Knowing where the ruling turns lets you spend the consultation on the conditions themselves.
Surcharge terms explained
- The twenty per cent surcharge
- The rule multiplying inheritance tax by 1.2 where property passes to someone other than the spouse or a first-degree relative (Article 18).
- Relative of the first degree
- A child or a parent. A grandchild is of the second degree, but falls outside the surcharge when standing in a deceased parent's place.
- Substituted succession
- Where the child who would have inherited has died first, their own child — the deceased's grandchild — takes their place as heir.
- Adopted grandchild
- A grandchild taken as an adopted child. Unless standing in a deceased parent's place, the surcharge applies even though they are adopted.
- Bequest
- Giving property by will. It may be made to someone who is not an heir.
- Share acquired
- The proportion of the estate that a person takes, settled by the division conference or by the will.
Frequently Asked Questions
Side Note — Why Are Only First-Degree Blood Relatives Exempt?
The 20% surcharge adjusts the tax burden based on how closely the recipient is related to the decedent. A spouse or child is generally seen as having directly supported the decedent's life and the building of the estate, while siblings or third parties often receive property through circumstances such as a will, so a heavier tax rate is applied in the interest of fairness.
Grandchildren receive special treatment for a similar reason. If assets pass directly from grandparent to grandchild, the inheritance tax that would normally apply once at the parent's generation gets skipped entirely. To prevent this kind of generation-skipping tax avoidance, a grandchild who is not a substitute heir (for example, one adopted by the grandparent while their own parent is still alive) is subject to the surcharge. But when a grandchild became a substitute heir because their parent passed away first, they are simply stepping into the position of the original heir (their parent), so they are exempt from the surcharge.
The 20% surcharge was created in the 1958 tax reform, and the 2003 reform later extended it to adopted grandchildren (grandchildren adopted by the deceased) who are not inheriting by representation. While the basic deduction amount and tax rate brackets for inheritance tax have been revised over the years, the underlying principle behind the surcharge — that transfers of property to people outside the immediate family should bear a somewhat heavier burden — has been maintained consistently.