This is perhaps a strange combination, child birth and child support, but it seems appropriate on this site. After all, if you become a parent, you have a responsibility to support your child. (NOW I THINK NOT. I NEED TO SEPARATE THESE.)

Japan has two ways to calculate child support. One is a set of charts allowing the calculation of a standard level of support based on the income of both parents and the age of the children. This tends to produce the higher of the two estimates but is by far the easiest to compute. We have what we believe to be copies of some of the charts, from 2003, listed below. If you need others, contact us, since we have them. The other ways is to apply a formula based on income and various expenses, including income taxes, social insurance, employment-related expenses and other special expenses, including living expenses, taken from standard tables based on where you live in Japan. This typically produces a much lower result than the standard levels of the charts. The final agreement, in cases where there is one, are often negotiated by the parents themselves with the courts and mediators serving only to "facilitate" the negotiation. This way, when one parent breaks the agreement, the other parent must start a whole new multi-year civil complaint rather than simply going to a judge that made the original order and asking them for help enforcing it. This is in the best interests of the judges and the legal system rather than the parents, since they are not bothered with complaints about court orders which they have no mechanisms to enforce. It would just make both them and the system look impotent. The moral is to force a judge to issue an order. The judge may be angry and give you less than what you asked for, but in some cases t may be better than more.

In the end, child support has typically been very low compared to Europe and America. Reportedly this is typically 30,000 to 40,000 yen/month for one child and 60,000 to 80,000 yen/month for two children, based on an average salaryman's income and non-working or part-time working mother. But this may have changed somewhat recently, as can be seen in the article below from the Japan Times.

Court-awarded child support and visitation rights are not enforced by the courts nor the police. Studies show that about 80 percent of separated fathers in Japan do not pay child support. Should the non-custodial parent stop paying, there are legal processes to garnish wages. If he or she works at a stable company, you might end up one of the lucky 20 percent. But if he or she does not have a regular job or tries to avoid paying by changing jobs or hiding assets, courts have virtually no power to force him to pay Conversely, if a custodial mother refuses to allow the father his visitation rights, their is very little he can do about it, except sue her which takes an inordinate amount of time. So visitation and child support often become tools of each of the parents to get what each should be doing anyways, but which courts cannot enforce.

Essays and Info

Birth With a Japanese Partner Within Wedlock Inside Japan
Birth With a Japanese Partner Within Wedlock Outside of Japan
Birth With a Japanese Partner Out of Wedlock in Japan
Birth With a Japanese Partner Out of Wedlock Outside of Japan
What to do IMMEDIATELY upon having a child with a Japanese citizen - make sure your are registered as the mother/father on the koseki of the Japanese. Get a copy of the koseki.
Calculating Child Support in Japan - includes charts
Here is a Japanese article on how to calculate child support payments. (2004.6.25) - From the Family Problems Information Center (seems to be a well known NGO.)
Online calculator for calculating child support in Japan (provided by a lawyer) English, but much more information on the original Japanese page is also available.
Recovery of Maintenance From Abroad
Child support and other public allowances
Collecting Withheld Child Support Payments in Japan

Articles

Japan lists father of child as 'not yet determined' due to 300-day divorce rule; Mainichi Daily News; August 8, 2007. The father of a child of a Japanese woman is listed on the British birth certificate and legally recognized in Britain and the British father. But in Japan, the child is listed on the ex-husband's family register because it was born within 300 days of the divorce. Also lists some rules from other countries.(cached copy)
'300-day kids' have to use mom's ex for passport; The Japan Times; May 3, 2007. (cached copy)
Single-mother child benefits hit record; The Asahi Shimbun; June 2, 2007. (cached copy)
Single moms get little support from state: report; Japan Times; June 2, 2007. (cached copy)
Tokyo ward office ordered to register girl after rejecting birth certificate; various sources; June 2007.
Justice Ministry to "help" by legitimizing just 10% of kids born less than 300 days after divorce; various sources; May 2007.
Majority favor reviewing law on birth of child within 300 days of divorce; The Mainichi Shimbun; May 1, 2007. (cached copy)
Unregistered kids to be provided services; The Japan Times; April 24, 2007. (cached copy)
LDP digs in heels against biological realities; The Japan Times; April 20, 2007. (cached copy)
Ministry OKs welfare payments for children without family registers; Mainichi Daily News; April 13, 2007. (cached copy)
Revisions to bill on children born after divorces to be deferred; Mainichi Daily News; April 11, 2007. (cached copy)
Govt changes child registry rules for divorcees; The Yomiuri Shimbun; Apr. 7, 2007. (cached copy)
Calls for changes to law on children born after divorces (EJ); The Mainichi Shimbun; March 20, 2007. (cached copy)
Several articles concerning children who cannot be registered on a koseki to their real father because they were born out of wedlock. (EJ). Feb - March, 2007. This also describes recent efforts to get passports for them and to file a lawsuit against the government. The "research Institute for Revision of Laws Concerning Parents and Children," a nonprofit organization based in Osaka is helping these women.
Troubleshooter: Girl hates visiting divorced father; The Daily Yomiuri; February 25, 2007. This advice column by a lawyer named Sachiyo Dohi, showed extreme naivety about why children sometimes claim to “hate” a non-custodial parent and about the realities of the Japanese legal system. The advice seemed more directed at provoking a legal dispute than at solving the problem in a way that was in the financial and psychological best interests of the child. (cached copy)
Allowances for single parents to be axed; Asahi Shinbun; December 1, 2006. The "mother-child family addition" payments, which offer between 20,020 yen and 23,260 yen per month for each child aged 15 or younger, will be phased out over the coming three years amid moves to slash fiscal 2007 expenditure on welfare by 40 billion yen. (cached copy)
Center planned to help single mothers collect payments from ex-husbands; The Asahi Shimbun; September 8, 2006. Contains some interesting statistics from a government survey, giving rates of child support payments by fathers, single mothers, child visitation. Also says that "Some 20.6 percent [of single mothers] said they wanted their former husbands out of their lives...". If you would expect a single mother to be more likely than a remarried mother to want help from the natural father, this gives us a conservative estimate of the overall rate of denied visitation.
Fatherless families to receive child-raising allowances; Kyodo; August 20, 2006. (cached copy)
Tommy Thompson: Japan needs international child support law (日本語版 / Japanese) Asahi Shinbun, English Edition; March 25, 2004. Secretary of the U.S. Department of Health and Human Services complains that Japan is not going to participate in the multilateral Hague treaty on recovery of child support after all. He also advocates signing the Hague Kidnapping convention and being able to enforce their own court orders. (cached copy)
Nonbinding child support standard set; Japan Times 11 June 2003. New public guidelines have been set for the amount of child support awarded in Japan. No info on enforcement or tying it to visitation rights. (cached copy)
Japanese Child Support Payments in 2002; J. Sean Curtin; Red Cross University. Summarizes state of alimony payments in Japan and men's ability to avoid them. (cached copy)
Japan Cuts Single-Mum Benefits, Blames Divorce Rate; Reuters; June 7, 2002. Japanese government has cut benefits to single mothers. Things start to change when the child is about 5 years old. Must read if custodial parent is a mother expecting support from the government. (cached copy)
In Japan, Moms Defy Tradition by Staying Single; WomensENews.org; May 3, 2002. More women in Japan are staying single with their children. They sometimes have it rough, so perhaps they would like to jointly press for new laws to encourage the father's participation, as an involved father is much more likely to willingly help financially also. (cached copy)
Six Percent of Single Moms Make Under JPY 3 Million; Daily Yomiuri; Sept 2001. The title says it all. (cached copy)

From 1996 CoCR

135. If a child is to recover maintenance in Japan in cases where his/her parents or other persons having financial responsibility for the child live in Japan. Maintenance for the child may be requested as: (i) part of marriage expenses during a matrimonial relationship; (ii) part of care-and-custody expenses for the child upon divorce; or (iii) performance of the parents' duty to raise the child. The means to recovery, as provided for in the Law for Adjudgement of Domestic Relations, include: (i) conciliation with regard to the said issues; (ii) claim for part of marriage expenses in a contentious case; (iii) claim for maintenance in a contentious case regarding the care and custody of the child; (iv) claim for maintenance in a contentious case concerning financial support for the child; (v) collateral claims upon a divorce suit under the provision of paragraph 1 of article 15 of the Law of Procedure in Actions Relating to Personal Status. Aside from judgements on the approval of collateral claims in divorce suits referred to in (v), protocols recording the consent and adjudications ordering the issuance of maintenance have the same effect as a title of obligation with executory power. Therefore, maintenance may be recovered by compulsory execution if the obligor fails to perform his/her obligation voluntarily. In addition to compulsory execution mentioned above, the Law for Adjudgement of Domestic Relations establishes a framework for ensuring the obligor meets his/her domestic liabilities, under which the Family Court may recommend or order the performance of the duty as ruled by conciliation or adjudgement. A total of 9,610 domestic cases involving recommendations to meet financial obligations were settled in 1994, out of which 6,411 cases were settled with liabilities fully or partially met. In cases where an agreement is concluded with regard to the payment of maintenance, the performance of the maintenance agreement may be demanded by instituting a lawsuit.

136. If a child is to recover maintenance in Japan in cases where his/her parents or other persons having financial responsibility for the child live in a different country from the child. As the case of trial on maintenance shall be handled by the Family Court exercising jurisdiction over the domicile of the adverse party (art. 94, para. 1, Regulations on Adjudgement of Domestic Relations), the child may demand conciliation or trial on maintenance to the Family Court exercising jurisdiction over the last domicile of his/her parents, etc. If the most recent address of a child's parents in Japan does not exist or cannot be identified, the child may demand conciliation or trial on maintenance to the Family Court exercising jurisdiction over the place where the property is situated in Japan or where the Supreme Court designates. If an agreement on the maintenance for the child is concluded between parents, etc. the child may enter an action to the District Court or Summary Court exercising jurisdiction over the place of the most recent address of the parents or the place of performing the duties under the maintenance agreement. If property of parents, etc. which may be attached exist in Japan, the child may enter an action to the District Court or Summary Court exercising jurisdiction over the region where the property is situated. Moreover, if a judgement or decision has been passed by any court in Japan on the payment of maintenance, the property may be subject to compulsory execution pursuant to the judgement or decision for the child.

137. With regard to the maintenance obligation, Japan acceded to the Convention on the Law Applicable to Maintenance Obligation in respect of Children on 22 July 1977 and the Convention on the Law Applicable to Maintenance Obligation on 5 June 1986.

Here is some text from a May 2003 Japan Federation of Bar Associations report to the UN Committee on the Rights of the Child (cached copy).

Part 1: Child-rearing allowance

1. In terms of the child-rearing allowance, efforts should be made to improve the amount, relax the income limitation, and improve the system for confirming actual income.

2. The provision, which stipulates that the allowance for a child born out of wedlock should be terminated once he/she is recognized, should be amended so that the child may receive it after such recognition.

3. The provision, which stipulates that the child-rearing allowance is not provided for a child whose parents are divorced if the father’s annual income exceeds a certain amount, should be abolished.

4. Motherless families who do not receive a child-rearing allowance under the existing law, should be made eligible for receiving it.

5. The provision, which stipulates that the child-rearing allowance will not be provided unless it is claimed within five years from when the requirements for payment are fulfilled, has no rational grounds and should be abolished.

1. 1. The JFBA’s report concerning the Initial Report on Japan recommended the following concerning the child-rearing allowance:

(1) The regulation to terminate the allowance for a child born out of wedlock when he/she is recognized should be amended so that the child may receive it following recognition.

(2) The provision, which stipulates that a child-rearing allowance is not provided for a child whose parents are divorced if the annual income of the father exceeds a certain amount, should be abolished.

(3) A motherless family for which child-rearing allowance is not provided for under the existing law should be included amongst those eligible to receive it.

(4) The provision, which stipulates that a child-rearing allowance will not be provided unless it is claimed within five years from when the requirements for the payment are fulfilled, has no rational grounds and should be abolished.

2. 2. With reference to the child-rearing allowance, the Government stated in Japan’s Second Report (para. 36) that: “The Child-Rearing Allowance scheme aims to enhance the economic stability and independence of fatherless families due to divorce or separation of the parents. The allowance is provided for those children that qualify under the policy in order to facilitate their welfare,” and explained the eligibility for receiving the allowance. The mother or legal guardian of a child, whose father is alive but lives in a separate household and is thus not responsible for supporting the child, is eligible for this allowance until the first day of March following the child's 18th birthday. In the case of handicapped children, the allowance is valid until the child's 20th birthday. From April 1999 a mother or legal guardian of a single child is eligible for a monthly allowance of 42,370 yen (full allowance), 28,350 yen (partial allowance). Those with two children will have an additional 5,000 yen. A family with three children will have an extra 3,000 yen added per child.

3. 3. With respect to the recommendations mentioned above, apart from some of the municipalities, which have decided to provide the child-rearing allowance to motherless families, nothing has improved.

On the contrary, the following modifications, which have on the whole reduced the standards, were made from August 2002. Specifically, the requirement regarding annual household income, which used to be less than 3,000,000 yen was modified to less than 3,650,000 yen, and the requirement regarding the minimum household income eligible for a full allowance, which used to be less than 2,048,000 yen, was modified to less than 1,300,000 yen.

In the case of a partial allowance, as the annual income increases by each 10,000 yen, approximately 170 yen will be deducted from the full monthly allowance. In the case of a fatherless household consisting of a mother and a child with an annual income of two million yen, the present full amount is 42,370 yen. In reality, however, according to this modification, 19,000 yen has been deducted.

Judging from the fact that the average annual income of fatherless households is about 2,350,000 yen, when considered with this modification, the amount of the child-rearing allowance has been reduced for many such households.

Moreover, according to this modification, when the benefit period exceeds five years, the allowance will be reduced to almost half. This measure will apply from next year.

4. 4. As mentioned in the JFBA Report concerning Japan’s Initial Report (para. 335), “in order to solve this problem fundamentally, the woman’s labor issue in Japan must be considered and rectified. For the moment, however, since the Child-rearing Allowance Scheme plays an important role in the economic independence of fatherless families following divorce, improvements such as higher allowances, loosening of the income level requirement, and revision of the system to conform with actual income, must be sought.”