Casual traders:
Expenses are miscellaneous itemized deductions subject to the 2% rule. This type of deduction was removed from federal taxes for 2018-2025, but may still be allowed in your state, so the program allows them to be listed. This would be expenses that are ordinary and necessary to generating investment income, that you would not incur if not for the investment activity. Most common would be subscriptions to investment news and analysis sites. To consider a computer a deductible expense, you would have to have some reliable written records showing what percentage of the time it is used for investing, and what percentage of the time it is used for other personal or non-investing purposes. Then you can deduct that percentage of the cost. But computers must be depreciated, rather than expensed (in most cases) so there's a lot of extra paperwork for not much extra reward. In theory, you can also deduct a portion of your home internet if you use it for research and trading, but again, you need some kind of reliable written record to allocate how much of your interest cost can be directly allocated to the trading activities. And remember, this only might be a deduction in some states, and the 2% rule means most people won't benefit even if it is allowed.
Self-employed:
If you are engaged in trading as an ongoing and regular business activity, you may be able to report yourself as self-employed on schedule C, which gives you a wider range of business expense deductions. This is too complicated for me to go into now, and trading has to be your main business activity, or at least a major and significant ongoing activity, to be counted as your business.
Investment interest:
There is a separate, special rule for deducting interest you pay on loans that you borrow so you can buy investments. I don't think you are referring to this, but we can explain further if this is the case.
