see this article - backdating documents is not allowed
your accountant is correct if you don't have an accountable plan.
https://proconnect.intuit.com/articles/home-office-deductions-expenses/
summary of article
2) The S corporation can pay you rent for the home office.
3) The S corporation can pay you for the costs of a home office under an "accountable" plan for employee business expense reimbursement.
The third option, being reimbursed under an accountable plan, provides the greatest tax savings. It is an excellent way to get money out of your closely-held corporation tax-free. The corporation can deduct the amount of the reimbursement and you do not have to report the payment on your personal income taxes.
The third option is better than having the corporation pay you rent for the home office. While your corporation can deduct the rent paid to you, you must report the rent as income on Schedule E.
