EXHIBIT 23 CONSENT OF INDEPENDENT AUDITORS We consent to the incorporation by reference in the Registration Statements (Form S-8 Nos. 333-78471, 333-78467, 333-78469 and 333-78473) pertaining to the 1998 Employee Stock Purchase Plan, the Amended and Restated 1997 Stock Incentive Plan, the Amended and Restated 1989 Stock Option Plan and the 1998 Director Stock Option Plan of Bottomline Technologies (de), Inc. of our report dated August 2, 1999, with respect to the financial statements and schedule of Bottomline Technologies (de), Inc. included in the Annual Report (Form 10-K) for the year ended June 30, 1999. /s/ Ernst & Young LLP Boston, Massachusetts September 24, 1999