20 CFR 322.4: Consideration of evidence.

(a) Initial proof. A claimant's certification that he or she did not work on any day claimed and did not receive income such as vacation pay or pay for time lost for any such day shall constitute sufficient evidence for an initial finding that no remuneration is payable or has accrued to him or her with respect to such day, unless a base year employer reports that he or she worked on days claimed or received payments that constitute remuneration as defined in this part, or unless there is other conflicting evidence.

(b) Investigation. When there is a question as to whether or not remuneration is payable or has accrued to a claimant with respect to a claimed day or days, investigation shall be made with a view to obtaining information sufficient for a finding.