Form W-3 is the transmittal that totals a batch of Forms W-2 and accompanies them to the Social Security Administration - not the IRS, which is a distinction that catches filers out. It is the W-2 equivalent of Form 1096. Filing W-2s electronically through SSA Business Services Online generates the totals automatically, so no separate W-3 is submitted; the form is a paper-filing artefact. Its totals are also what the IRS reconciles against the four quarterly Forms 941, and a mismatch between them is one of the more common triggers for correspondence.
Whether you deposit monthly or semiweekly depends on your lookback period, not on this form. Publication 15 (Circular E) sets the rule, and it is worth checking each year - the schedule can change when your liability does.
IRS Publication 15No. Electronic filing through SSA Business Services Online produces the totals itself, so there is no separate W-3 to submit.
No. W-2s and W-3 go to the Social Security Administration. The IRS receives the data from SSA and reconciles it against your Forms 941.
Expect a notice. The two are reconciled, and a difference between the annual W-3 total and the sum of the four quarterly 941s is one of the most common causes of employment tax correspondence.