To write a child support agreement letter, determine the amount of support that legislation prescribes based on location and income. Contact the other parent or their lawyer to ensure that they are in agreement with these terms. Then, write a letter to a judge, the other parent's lawyer or the parent themselves stating the amount to be paid and when payments shall be made, as reported by Find Law.
Wikipedia reports that, usually, the non-custodial parent makes payments to the custodial parent. There are three general models that states and Native American tribes use in the calculation of child support obligations. These include the income shares model, the percentage of income model and the Melson formula. The Melson formula is similar to the percentage of income model except that it includes a standard-of-living adjustment.
Once the amount of support that legislation requires to be paid is determined and the other parent agrees, a business letter may be written. It should include the name and address of the person writing the letter, the name and address of the person to which the letter is addressed, the date, a subject line, a formal salutation and a letter body detailing how much child support shall be paid and when. Sign the letter cordially using "Yours Truly" or "Best Regards." Sample letters are available on the Internet from Letters Free, Live Career and other sample letter providers.