Your doctor should not write an abatement letter. Your tax advisor should do that, using the doctoru2019s letter as support.The doctoru2019s job is to set forth the medical facts found after examining you, and his/her opinion as to the degree to which that medical condition prevented you from performing certain tasks.Your tax advisor would then use that letter in support for making a reasonable cause argument.If the doctoru2019s letter looks like it is taking an advocate position, rhe IRS may question its validity.