Thank you for the detailed responses.
@Guilherme got it right; the IRS does not know I sold a horse and that is not what triggered the audit. The audit is a compliance audit which was most likely triggered by an error that I made on my return (which did not result in me owing anything more or less and was a reporting error, reported MSRP value of year-end business inventory and not cost value) which was corrected months before notice of the audit. As it was explained to me, the IRS randomly selects returns for this type of audit when they decide that it is likely that there are more mistakes to be uncovered… so I was selected from this pool.
The agent is going through my personal bank statements and wants to know what every single deposit into my account is, so I have to explain the +$6500 = horse sale since she asked what this deposit was. I’m a little blindsided by this because I prepared to back up every single penny spent on my business that year, and didn’t even remember that I sold my horse until asked to justify the +$6500. My accountant has worked with this agent before and said that she is just super meticulous, and if we keep giving her info that she requests without an attitude that she will be reasonable.
So far the audit is resulting in the IRS making minor adjustments in my favor, so I want to be prepared if the agent sees an opportunity to turn the tables.
My horse was my pet/hobby when I was a student. I did not participate in any activities where I made money from him, and we did not partake in activities where I won prize money. Horse expenses were never claimed in any prior taxes. My current self-employment is in fashion retail and has nothing to do with horses.
Thank you for all of the advice though. This is very annoying and a big waste of everyone’s time and money (mine and the government’s), and I look forward to it being concluded.
PS. My accountant is a CPA and has been dealing directly with the IRS agent without me. He was also the one who corrected the mistake on my return for me so he knows my business finances up and down. I like him very much and he knows how to work with this specific agent which I think it helpful, just has never had a client with a horse sale.