Jan 4 (Reuters) - Human resources and payroll software maker Justworks said on Tuesday it was aiming for a valuation of up to $2 billion in its initial public offering in the United States. The company, backed by Bain Capital, said it was offering 7 million shares at between $28 and $32 per share. That would fetch Justworks $224 million at the top end of the price range. Justworks also counts Thrive Capital and Index Ventures among its investors. Its shares will be listed on the Nasdaq under the symbol "JW", the company said in a filing. Founded in 2012, the New York-based company lets small and medium-sized businesses to handle payroll, benefits, compliance and human resources. Goldman Sachs, J.P. Morgan and BofA Securities are the lead underwriters for the offering.