Short answer. Substituted service: you may deliver the copy to the clerk of court, together with proof that both personal service and service by mail failed because the party's or counsel's office and residence are unknown. Service is complete the moment that delivery to the clerk is made.

What the law says

If service of pleadings, motions, notices, resolutions, orders and other papers cannot be made under the two preceding [S]ections, the office and place of residence of the party or his or her counsel being unknown, service may be made by delivering the copy to the clerk of court, with proof of failure of both personal service and service by mail. The service is complete at the time of such delivery.

Rule 13, Section 8 — Substituted service. Read the full provision →

When this fallback applies

This mode of service only opens up once the two ordinary channels — personal service and service by mail — cannot be carried out, specifically because the office and place of residence of the party or counsel are unknown. It is not a shortcut a party can reach for whenever mailing or hand-delivery is merely inconvenient or slow; the unknown whereabouts of the person to be served is the specific condition the rule requires before substituted service through the clerk of court becomes available at all.

What has to be delivered, and to whom

The serving party delivers the copy of the pleading, motion, notice, resolution, order, or other paper to the clerk of court, rather than to the opposing party or counsel directly. That delivery must be accompanied by proof showing that both personal service and service by mail were attempted and failed for the stated reason — an unknown office and residence. Without that proof of the two prior failed attempts, delivery to the clerk alone would not establish that service was validly made under this provision.

When service is treated as complete

The rule fixes the moment of completion precisely: service is complete at the time the copy is delivered to the clerk of court, not when, or if, the intended recipient later actually learns of it. This matters a great deal for computing any period that runs from the date of service, since the clock starts running from that delivery to the clerk, regardless of whether the party being served ever becomes aware of the filing.

Why this exists

The provision exists because a case cannot simply stall whenever a party or counsel cannot be located through the usual means. By allowing delivery to the clerk of court as a last resort, once personal service and mail have both genuinely failed, the Rules keep pleadings, orders, and notices moving through the case record even when the person meant to receive them cannot be found through ordinary diligence.

Related provisions

Note. Statute text quoted on this page is reproduced from the official enactment and is linked to the full provision. The explanation around it is general legal information from Vivas & Nobles Law Office, not legal advice. Whether it applies to your situation depends on facts only a lawyer reviewing them can assess.