About Taxable Income (PDF) Form 945EZ, Payment of Child Support Obligation Tax (PDF). (See IRS Tax-Related Publications for other forms used in the U.S.— For Form 540, Payment and Collection of Child Support Obligation Tax (PDF), go to. Last revised: October 31, 2017. Updated: November 28, 2017. IRS Taxpayer Advocate Service (TAXA) Online Customer Care. Online chat and online FAQs with Taxable help line. Taxpayer Advocate Service (TAXA) Online Customer Care. Phone: Phone (Toll Free): Taxpayer Advocate Service (TAXA) Contact Information Address: P.O. Box 2000 Alexandria, VA 22 Phone: Toll Free: Taxpayer Advocate Service Contact Information, (TAR) Address: 3025 Lake Charles Ct. Alexandria, VA 22 Phone: Toll Free: IRS Resources for Taxpayers (PDFs): Taxpayer Education and Assistance Act The IRS recently published a report “Taxpayer Education and Outreach” (PDF) outlining the resources available to taxpayers. It is available in the following formats: The Report is also available in printed form. If you want to have it mailed to you, the best way to do so is to send your request to: Revenue Service. Internal Revenue Service P.O. Box 50950 Baltimore, MD 2 Taxpayers who receive this document as an attachment will have the option to e-file it with a 1040-ES. The IRS Publication #55 (PDF) : the Taxpayer Credit guide (for tax years 1990–2015) is another great resource. This publication lists all tax credits and credits related to federal income taxes and includes the tax credit rate amounts of the current tax year. If the current tax return includes an estimated tax return, this publication will also show the refund amounts.