When will the delivery of a check produce the effect of payment even if the same had not been encashed?

If the debtor was prejudiced by the creditor's unreasonable delay in presentment. Acceptance of a check implies an undertaking of due diligence in presenting it for payment. If no such presentment was made, the drawer cannot be held liable irrespective of loss or injury sustained by the payee. Payment will be deemed effected and the obligation for which the check was given as conditional payment will be discharged. (Pio Barretto Realty Corp. v. CA, G.R. No. 132362, June 28, 2001).