How Do I Write A Letter To The IRS On Behalf Of A Customer Stating That She Has Paid For An Event?

I wish I knew what you meant by "an event". You have to give the IRS the person's name, social security number, and the tax year in question. You should provide any documentation that the taxpayer has that will back up the claim that payment was already made. In addition, you should provide the taxpayer's address because the IRS cannot respond directly to you unless you have her Power of Attorney or written consent from the taxpayer that the IRS may discuss the matter with you. All taxpayer information is confidential and may not be shared with a third party without consent from the taxpayer.