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Starting 1993, employment placement service was included within the meaning of "sale" and "selling" [Section 5739.01(B)(3)(e), Ohio Revised Code] and became a transaction upon which Ohio Sales Tax is to be charged. "Employment placement service" is defined in Section 5739.01 (KK) O.R.C. as "locating or finding employment for a person or finding or locating an employee to fill an available position."

The nature of the service covered by these sections and the "price" upon which tax is calculated can be readily understood. Employment placement service is a narrowly defined term and the tax on it applies to the fees, commissions, or other charges that a person pays for securing employment; that an employer pays for finding a person for a position; or that a person or company pays for finding or locating a position for a person.

"Employment service" does not include - and not subject of sales tax:
1.Acting as a contractor or subcontractor, where the personnel performing the work are not under the direct control of the purchaser.
2.Medical and health care services.
3.Supplying personnel to a purchaser pursuant to a contract of at least one year between the service provider and the purchaser that specifies that each employee covered under the contract is assigned to the purchaser on a permanent basis.
4.Transactions between members of an affiliated group, as defined in division (B)(3)(e) of this section.
5.Transactions where the personnel so provided or supplied by a provider or supplier to a purchaser of an employment service are then provided or supplied by that purchaser to a third party as an employment service, except "employment service" does include the transaction between that purchaser and the third party.

Thus - if you separately pay to contractors for their services that amount is not taxable.
Correspondingly - see also - http://www.ohiostatetaxblog.com/index.php?option=com_content&view=article&id=52:are-you-paying-ohio-sales-tax-on-leased-employees&catid=47:ohio-sales-and-use-tax&Itemid=59
http://tax.ohio.gov/divisions/communications/information_releases/sales/st199301.stm
http://tax.ohio.gov/divisions/communications/information_releases/sales/st200002.stm
http://www.vertexinc.com/ResourceCenter/articles/2007/March/services.asp
http://www.ohiochamber.com/dococc/SYSTEM-IssueCenter/Taxation/pdf/House%20Tax%20Study%20Testimony%20092211.pdf
http://tax.ohio.gov/divisions/communications/information_releases/sales/st200002.stm