Do I need to file a tax return as a dependent if my net capital gains are close to $0 but my trading volume is very high?

No, you do not. As you quote yourself - you are way below the profit limits. You ALSO have a pathetic low volume. Yes, 15k will look high for you, but any software that would (assuming one would) go through the trades will NOT look for someone with 15k trading Volume IN A YEAR.

I have to congratulate you for trading SMALL (it is obvious your account is small), but assuming 15k trading volume will be something the IRS looks at is delusional. They will see a TON of small trades - extremely small trades, because to get 15k with day trading IN A YEAR means your average trade must have been in the area of 10 USD or 20 USD. This is typical for learning or testing and not does not really show up.

They are way more interested in those people who actually have volumes giving them rebates (as in: hundreds of thousands or even millions of USD per MONTH).

The problem you face is that if other people/companies file forms related to your transactions that make it appear that you should file, then you have to file to be able to prove you owe no income tax.

Imagine this scenario. A person is married, and has a kid. They know that if they itemize, and take everything they are entitled to they won't owe any taxes. They won't face interest or penalties because they are getting a refund. Of course a few months after the deadline the IRS matches their 1099's and W-2 and doesn't find a return. So they calculate it. Of course they don't include the child, and they assume the standard deduction. Now they calculate that you owe. So they send you a notice, and include interest and penalties. So you end up filing to prove you don't owe anything.

You also only quote part of the rule:

You must file a return if any of the following apply.

1. Your unearned income was over $1,100.
2. Your earned income was over $12,200.
3. Your gross income was more than the larger of

• a. $1,100, or
• b. Your earned income (up to $11,850) plus $350.

Now you are OK if your earned income is zero, but sometimes people have less than $12,200 in earned income and less than $1,100 in unearned income and think they are safe, but then get tripped by 3b.

The IRS also discusses who should file

Form 1099-B received.

Even if you aren't required to file a return, you should consider filing if all of the following apply.

• You received a Form 1099-B, Proceeds From Broker and Barter Exchange Transactions (or substitute statement).

• The amount in box 1d of Form 1099-B (or substitute statement), when added to your other gross income, means you have to file a tax return because of the filing requirement in Table 1 or Table 2 that applies to you.

• Box 1e of Form 1099-B (or substitute statement) is blank.

In this case, filing a return may keep you from getting a notice from the IRS.

It doesn't match your situation exactly but it does discuss a reason to file could be to avoid a notice.