It is a form that needs to be filed. You need to read about forms 940, 941, W2, and W3. There may be additional state and local filing and withholding requirements.
Or pay a small fee to a payroll processor to do this for you (and help you comply with other mandatory requirements).
After reading your other questions (here, here), I have better context now and see that you don't really understand what you're doing (no offense, you're not the first and not the last).
So a couple of clarifications:
It's not you paying yourself the salary, it's your LLC, which is a completely separate legal entity. You've elected it to also be treated as a completely separate entity for tax purposes (you didn't have to, but you explicitly told the IRS that you wanted to). As the result, you need to completely separate the concept of
number41 the person and
Number41 LLC the company - they're not at all the same.
With that in mind... The company has to withhold taxes from the salary it pays to the employee, and remit the taxes on behalf of that employee to the IRS (and State). It is the company's legal obligation, not yours.
Forms 940 and 941 are used to report how much money was withheld and remitted. These are usually filed quarterly (with some exceptions).
Forms W2 and W3 are used to report how much each employee earned, how these earnings are categorized, and how much money was remitted on their behalf to the IRS and the State. These forms are usually filed annually. A copy of form W2 is then being furnished to each of the employees.
Or is there no difference in this case? What would differentiate "withheld" taxes from estimated tax payments?
Withholding is the obligation of the employer,
Number41 LLC. Estimated tax payments are the obligation of the emploee,
M. Number41. The obligation to pay estimates may be satisfied through salary withholding made by your employer on your behalf, but not the other way around.