16 Pa. Stat. § 1750
The controller or the county commissioners in counties having no controller shall scrutinize, audit and decide on all bills, claims and demands whatsoever against the county, except such as are otherwise provided for in this subdivision. All persons having such claims shall first present the claims to the controller or to the county commissioners and, if required, make oath or affirmation before the controller or commissioners to the correctness of the claims. The controller or the commissioners, as the case may be, may require evidence, by oath or affirmation, of the claimant and otherwise that the claim is legally due and that the supplies or services for which payment is claimed have been furnished or performed under legal authority. The controller or commissioners may inquire or ascertain whether any officer or agent of the county is interested in the contract under which any claim may arise, or has received or is to receive any commission, consideration or gratuity relating thereto, or whether there has been any evasion of the provisions of this act by making two or more contracts for small amounts which should have been in one. If either shall find that any such officer or agent is so interested, except as provided under section 1806, or that there has been any evasion, the controller or commissioners shall refuse to approve the claim.
16 P.S. § 1750