26 C.F.R. § 1.105-2
Section 105(b) provides an exclusion from gross income with respect to the amounts referred to in section 105(a) (see § 1.105-1 ) which are paid, directly or indirectly, to the taxpayer to reimburse him for expenses incurred for the medical care (as defined in section 213(e)) of the taxpayer, his spouse, and his dependents (as defined in section 152). However, the exclusion does not apply to amounts which are attributable to (and not in excess of) deductions allowed under section 213 (relating to medical, etc., expenses) for any prior taxable year. See section 213 and the regulations thereunder. Section 105(b) applies only to amounts which are paid specifically to reimburse the taxpayer for expenses incurred by him for the prescribed medical care. Thus, section 105(b) does not apply to amounts which the taxpayer would be entitled to receive irrespective of whether or not he incurs expenses for medical care. For example, if under a wage continuation plan the taxpayer is entitled to regular wages during a period of absence from work due to sickness or injury, amounts received under such plan are not excludable from his gross income under section 105(b) even though the taxpayer may have incurred medical expenses during the period of illness. Such amounts may, however, be excludable from his gross income under section 105(d). See § 1.105-4 . If the amounts are paid to the taxpayer solely to reimburse him for expenses which he incurred for the prescribed medical care, section 105(b) is applicable even though such amounts are paid without proof of the amount of the actual expenses incurred by the taxpayer, but section 105(b) is not applicable to the extent that such amounts exceed the amount of the actual expenses for such medical care. If the taxpayer incurs an obligation for medical care, payment to the obligee in discharge of such obligation shall constitute indirect payment to the taxpayer as reimbursement for medical care. Similarly, payment to or on behalf of the taxpayer's spouse or dependents shall constitute indirect payment to the taxpayer.
26 C.F.R. §1.105-2