CLSI accepts online payment using any major credit card.

Instructions for paying an INVOICE:

  1. Enter your invoice number(s) in the Reference Number field below. If you are attempting to pay multiple invoices, please enter each invoice number separated by a common.
  2. Click “Pay Now”. (You will be redirected to our third-party secure website for the transaction.)

Instructions for paying a RETAINER:

  1. Enter your project or proposal ID in the Reference Number field below.
  2. Click “Pay Now”. (You will be redirected to our third-party secure website for the transaction.)
Reference Number(s):