When are employers required to mail copies of Form W-4 to the IRS?

Employers are required to mail copies of Form W-4 to the IRS when the IRS specifically requests it in writing. This requirement ensures that the IRS can verify withholding amounts and compliance with tax regulations. It serves as a safeguard for ensuring correct tax withholding, especially in instances where there's a need to confirm the allowances claimed by the employee or to address discrepancies.

The other situations, such as claiming more than a certain number of allowances, claiming exempt status from withholding, or specific personal circumstances, do not inherently trigger a mandatory submission to the IRS without a direct request. Generally, submitting Form W-4 is primarily for the employer's records and for payroll processing unless instructed otherwise by the IRS. Hence, the only correct instance from the options provided is when the IRS explicitly requests the form in writing.