While you won’t submit your expense documentation with your tax return, you will need it to 1) know how much you can deduct from your business income, and 2) to back up those deductions during an audit.
A good way to think about claiming tax deductions is that the more documentation, the better. The documentation you keep should provide the full context of your purchases to the IRS, should you ever be audited. The details that the IRS would want to know include:
-Time and date of the expense
-Description and business purpose of the expense
-Name of the vendor
-Amount of the expense
Ideally, you'd keep receipts (or pictures of receipts) from each of your business purchases, and keep detailed notes on how you use each item that you buy. However, with good cause the IRS may accommodate particular circumstances that hindered your ability to preserve adequate records.
It’s recommended that you keep your documentation for at least three years after the end of the tax year. Once you've filed your returns, the IRS has up to three years to review your tax returns and assess any additional taxes owed. However, it can take up to six years to make a tax assessment if they determine that you omitted a substantial amount of income from your return.