(a) Federal Insurance Contributions Act and Railroad Retirement Tax Act—(1) Overcollection ascertained before return is filed. (i) If an employer during any return period collects from an employee more than the correct amount of employee Federal Insurance Contributions Act (FICA) tax under section 3101 or employee Railroad Retirement Tax Act (RRTA) tax under section 3201, and if the employer ascertains the error before filing the return on which the employee tax is required to be reported, repays or reimburses the amount of the overcollection to the employee before filing the return for such return period, and obtains and keeps as part of its records the written receipt of the employee showing the date and amount of the repayment or evidence of reimbursement, the employer shall not report on any return or pay to the IRS the amount of the overcollection.

(ii) Any overcollection not repaid or reimbursed to the employee as provided in paragraph (a)(1)(i) of this section shall be reported and paid to the IRS on the return for reporting such tax for the return period in which the overcollection is made. However, the reporting and payment of the overcollection may subsequently be treated as an overpayment error ascertained after the return is filed for purposes of paragraph (a)(2) of this section.

(iii) For purposes of this paragraph (a)(1), an error is ascertained when the employer has sufficient knowledge of the error to be able to correct it.

(2) Error ascertained after return is filed. (i) Except as provided in paragraph (a)(2)(ii) of this section, if an employer files a return for a return period on which FICA tax or RRTA tax is reported, collects from an employee and pays to the IRS more than the correct amount of the employee FICA or RRTA tax, and if the employer ascertains the error after filing the return and within the applicable period of limitations on credit or refund, the employer shall repay or reimburse the employee in the amount of the overcollection prior to the expiration of such limitations period. However, this paragraph (a)(2) does not apply to the extent that, after reasonable efforts, the employer cannot locate the employee, or the employee does not provide the employer with the written statement required by § 31.6413(a)-1(a)(2)(iv). This paragraph (a)(2) has no application in any case in which an overcollection is made the subject of a claim by the employer for refund or credit under the procedure provided in § 31.6402(a)-2.

(ii) If an employer files a return for a return period on which Additional Medicare Tax under section 3101(b)(2) or section 3201(a) is reported, collects from an employee and pays to the IRS more than the correct amount of Additional Medicare Tax required to be withheld from wages or compensation, and if the employer ascertains the error after filing the return but before the end of the calendar year in which the wages or compensation were paid, the employer shall repay or reimburse the employee in the amount of the overcollection prior to the end of the calendar year. However, this paragraph does not apply to the extent that, after reasonable efforts, the employer cannot locate the employee.

(iii) If the employer repays the amount of the overcollection to an employee, the employer shall obtain and keep as part of its records the written receipt of the employee, showing the date and amount of the repayment.

(iv) If the employer reimburses the amount of the overcollection to an employee, the employer shall keep as part of its records evidence of reimbursement. However, for purposes of overcollected Additional Medicare Tax under section 3101(b)(2) or section 3201(a), the employer shall reimburse the employee by applying the amount of the overcollection against the employee FICA or RRTA tax which attaches to wages or compensation paid by the employer to the employee in the calendar year in which the overcollection is made. The employer shall reimburse the employee by applying the amount of the overcollection against the employee FICA or RRTA tax which attaches to wages or compensation paid by the employer to the employee prior to the expiration of the applicable period of limitations on credit or refund. If the amount of the overcollection exceeds the amount so applied against such employee tax, the excess amount shall be repaid to the employee as required by this section.

(v) If, in any calendar year, an employer repays or reimburses an employee in the amount of an overcollection of employee FICA or RRTA tax that was collected from the employee in a prior calendar year, the employer shall obtain from the employee and keep as part of its records a written statement that the employee has not claimed refund or credit of the amount of the overcollection, or if so, such claim has been rejected, and that the employee will not claim refund or credit of such amount. For this purpose, a claim for refund or credit by the employee includes instances in which the employee has included an overcollection of employee FICA or RRTA tax in computing a special refund (see § 31.6413(c)-1). This paragraph (a)(2)(v) does not apply for purposes of overcollected Additional Medicare Tax under section 3101(b)(2) or section 3201(a) which must be repaid or reimbursed to the employee in the calendar year in which the overcollection is made.

(vi) For purposes of this paragraph (a)(2), an error is ascertained when the employer has sufficient knowledge of the error to be able to correct it.

(vii) For the period of limitations on credit or refund of taxes, see § 301.6511(a)-1.

(viii) For corrections of FICA and RRTA tax paid under the wrong chapter, see § 31.6205-1(b)(2)(ii) and (iii) and § 31.3503-1.

(b) Income tax withheld from wages—(1) Overcollection ascertained before return is filed. (i) If an employer during any return period collects from an employee more than the correct amount of tax required to be withheld from wages under section 3402, and if the employer ascertains the error before filing the return on which such tax is required to be reported, repays or reimburses the amount of the overcollection to the employee before filing the return for such return period and before the end of the calendar year in which the overcollection was made, and obtains and keeps as part of its records the written receipt of the employee showing the date and amount of the repayment or evidence of reimbursement, the employer shall not report on any return or pay to the IRS the amount of the overcollection.

(ii) Any overcollection not repaid or reimbursed to the employee as provided in paragraph (b)(1)(i) of this section shall be reported and paid to the IRS on the return for reporting such tax for the return period in which the overcollection is made. However, the reporting and payment of the overcollection may subsequently be treated as an overpayment error ascertained after the return is filed for purposes of paragraph (b)(2) of this section.

(iii) For purposes of this paragraph (b)(1), an error is ascertained when the employer has sufficient knowledge of the error to be able to correct it.

(2) Error ascertained after return is filed. (i) If an employer files a return for a return period on which tax required to be withheld from wages is reported, collects from an employee and pays to the IRS more than the correct amount of the tax required to be withheld from wages, and if the employer ascertains the error after filing the return but before the end of the calendar year in which the wages were paid, the employer shall repay or reimburse the employee in the amount of the overcollection prior to the end of the calendar year. However, this paragraph does not apply to the extent that, after reasonable efforts, the employer cannot locate the employee.

(ii) If the employer repays the amount of the overcollection to an employee, the employer shall obtain and keep as part of its records the written receipt of the employee, showing the date and amount of the repayment.

(iii) If the employer reimburses the amount of the overcollection to an employee, the employer shall keep as part of its records evidence of reimbursement. The employer shall reimburse the employee by applying the amount of the overcollection against the tax under section 3402, which otherwise would be required to be withheld from wages paid by the employer to the employee in the calendar year in which the overcollection is made. If the amount of the overcollection exceeds the amount so applied against such tax, the excess amount shall be repaid to the employee as required by this section.

(iv) For purposes of this paragraph (b)(2), an error is ascertained when the employer has sufficient knowledge of the error to be able to correct it.

(c) Effective/applicability date. Paragraph (a) of this section applies to adjusted returns filed on or after November 29, 2013.