You may accept payment from a non-Federal source or authorize an employee and/or the employee's spouse to accept payment on your behalf only when-

(a) You have issued the employee (and/or the employee's spouse, when applicable) a travel authorization before the travel begins;

(b) You have determined that the travel is in the interest of the Government;

(c) The travel relates to the employee's official duties; and

(d) The non-Federal source is not disqualified due to a conflict of interest under §304-5.3.