This letter will confirm     [individual's]     telephone conversation with you today concerning an increase in our billing rate to     [amount]     per hour， effective [date] It is necessary that we request this increase due to a rise in the cost of conducting our business.  We are faced with an increase in payroll¹ taxes and insurance， along with an increase in our overhead costs.  In addition to the above，we also seek a modest profit.

　　Attached are copies of our service agreement and we request that you sign one copy and return it to us indicating your approval of this new rate