A practical, everything-you-need-to-know guide in the Philippine setting. This is general information, not legal advice.

1) Understand what you received

Subpoena = a compulsory order to appear and/or bring documents.

Subpoena ad testificandum — compels a person to appear and testify before a court, tribunal, prosecutor, or authorized agency.
Subpoena duces tecum — compels a person to produce specific documents or things (often together with personal appearance).

Philippine courts (trial and appellate), prosecutors (for preliminary investigation), and many quasi-judicial agencies (e.g., Ombudsman, COA, DOLE, SEC under their charters) may issue subpoenas.

2) Do an immediate validity check (same day)

Work through this quick screen:

Authority & jurisdiction
- Is it signed or issued by a judge/authorized officer or an empowered agency?
- Is the venue within the issuing body’s jurisdiction, and is there a pending case or investigation identified?
Form & particulars
- Case title/docket number (or investigation reference).
- Specific date, time, and place of attendance/production.
- For duces tecum: documents/items are described with reasonable particularity (no fishing expeditions).
Proper addressee & service
- Served on the actual witness (or authorized corporate officer/representative).
- Mode of service that reasonably ensures receipt (typically personal service; sometimes registered mail or courier per directives).
Reasonableness
- Time to comply is not unreasonably short.
- Scope is relevant to the matter and not oppressive (e.g., decades of files with 3 days’ notice).
Fees/allowances (for witnesses)
- Court attendance typically entitles a witness to statutory witness fees and transportation per the Rules of Court and relevant circulars (amounts are modest). Lack of tender isn’t always fatal, but note it when planning your response.

If any of the above fails, consider moving to quash/modify (see §6).

3) Calendar the deadlines and preserve evidence

Diary the appearance/production date immediately and work backward for prep time.
Issue a legal hold (especially for businesses): suspend routine deletion, notify custodians, and secure devices/files to prevent spoliation.
Identify whether any backups, cloud drives, messaging apps, or third-party custodians (e.g., payroll providers) hold responsive data.

4) Map the stakeholders and risks

Who is the witness? Employee, officer, or third party?
Nature of exposure: civil, criminal, administrative, tax, regulatory.
Parallel proceedings? The same facts may be under investigation elsewhere; coordinate a unified approach.
Confidentiality & privilege: flag potential privileged or confidential material (see §7).

5) Prepare to comply (default posture)

Even when you will object to some parts, prepare for good-faith, partial compliance:

For testimony: gather facts, records, timelines; rehearse truthful, concise answers.
For documents: collect, de-duplicate, and review for responsiveness, privilege, and personal data. Create a production log.

Production mechanics (duces tecum):

Organize by request number or custodian/date.
Use cover letter with case caption identifying what is produced and any withheld items (and the basis).
If electronic files are requested, ask (or default to) common formats (PDF, XLSX, native with metadata if specified).
Consider on-site inspection or certified copies when originals are sensitive.

6) If necessary, move to quash or modify the subpoena

Grounds commonly raised in PH practice:

Lack of authority/jurisdiction or improper service.
Unreasonableness/oppressiveness (overbroad scope, disproportionate burden, insufficient time).
Irrelevance or lack of particularity (especially for duces tecum).
Protected material (privileged communications; trade secrets; state secrets).
Non-possession / non-control of requested items (explain who has them, if known).

Timing: File as soon as practicable and before the compliance date. Ask for urgent relief (e.g., suspension of compliance pending resolution).

Alternatives to quashal:

Narrowing (limit time frame, custodians, or document categories).
Protective orders (e.g., in-camera review, confidentiality undertakings, redactions).

7) Key rights and privileges to assess

Right against self-incrimination (Const., Art. III, §17):
- A witness cannot be compelled to give testimonial evidence that may incriminate them.
- This is claimed question-by-question while testifying, or identified in a written objection for documents tightly linked to testimonial compulsion.
Attorney–client privilege: communications made in professional confidence for legal advice are protected; privilege belongs to the client.
Spousal communications privilege (and disqualification rules); priest-penitent; public officer privilege for state secrets; trade secrets/confidential business information may be protected via balancing tests and protective orders.
Third-party/corporate records: a corporation generally cannot claim personal self-incrimination; a custodian may be compelled to produce corporate records if otherwise proper.
Data Privacy Act (DPA): a lawful subpoena is a recognized legal basis for processing/disclosure. Still, apply data minimization and redact non-responsive sensitive data where feasible, and protect transmissions.

8) Special contexts

A) Prosecutor’s subpoena (preliminary investigation)

Respondents are subpoenaed to submit counter-affidavits and evidence and may be directed to appear for clarificatory questions.
Failure to comply can lead to a resolution on available evidence and, where appropriate, filing of information in court.

B) Agency/Quasi-judicial subpoenas

Many regulators have express subpoena powers under statute or rules.
Non-compliance risks contempt, administrative sanctions, or adverse inferences in the administrative case.

C) Court subpoenas (civil or criminal)

Non-appearance or non-production without adequate cause may result in indirect contempt and, in practice, a bench warrant to compel attendance.
Courts can allow remote testimony (e.g., videoconferencing) upon motion and for good cause.

9) What happens if you ignore it?

Contempt (fines and/or detention until compliance).
Adverse procedural consequences (e.g., striking of pleadings in some contexts, evidence taken ex parte).
Compulsory processes (warrants to compel attendance; sheriff enforcement).
In agency settings, administrative penalties and possible referral to prosecutors.

10) Practical timelines (checklist)

Day 0–1

Validate subpoena (see §2).
Calendar deadlines; notify counsel; issue legal hold.

Day 1–3

Scoping meeting (facts, custodians, data sources).
Start collection and privilege review.
Draft objections/grounds for narrowing.

Day 3–7

File motion to quash/modify if needed; request interim relief.
Prepare witness outline and exhibits.

Before deadline

Serve production (with cover letter/log) or appear to testify.
If still negotiating scope, document the compromise in writing.

11) How to appear and testify (ad testificandum)

Arrive early with government ID and the subpoena.
Take the oath and listen carefully; answer truthfully and only the question asked.
If a question risks self-incrimination or invades privilege, state the objection/claim of privilege clearly.
You can ask to review documents before answering about them.
Maintain composure; request to see the record if misquoted.

12) How to produce documents (duces tecum)

Use a transmittal letter that: (a) identifies the subpoena, (b) lists what you are producing, (c) states any objections/withheld items and why, and (d) requests acknowledgment of receipt.
If originals are requested but risky to release, offer inspection or certified true copies.
Apply redactions narrowly and explain them in your log.
Keep a complete copy of what you produced.

13) Companies & organizations: extra duties

Appoint a records custodian and corporate representative (Rule 130 allows testimony of a representative on corporate knowledge).
Implement document retention and email/chat archiving policies; suspend auto-deletion once subpoenaed.
Coordinate with IT for defensible collection and metadata preservation.
Consider confidentiality undertakings or protective orders when trade secrets or customer data are involved.

14) Common mistakes to avoid

Waiting until the eve of the deadline to raise overbreadth/privilege issues.
Producing data without review, exposing privileged or personal data unnecessarily.
Selective compliance without disclosure—courts expect transparency about what is withheld and why.
Assuming a prosecutor’s subpoena can be ignored because it’s “not a court”—it is compulsory under the Rules on preliminary investigation.
Letting custodians self-collect without oversight, risking gaps or spoliation.

15) Templates (short forms)

A) Cover/Transmittal Letter (duces tecum)

[Date]

[Issuing Body/Case Caption]
Re: Subpoena Duces Tecum dated [date]; [Case/Ref. No.]

We respectfully produce the following materials responsive to the subpoena, as itemized in the attached index. We maintain the objections stated below and withhold items identified in the privilege/redaction log, produced concurrently.

We request acknowledgment of receipt.

Respectfully,
[Name/Title/Contact]

B) Objections / Motion to Modify (outline)

I. Background and timeline
II. Legal standard (relevance, particularity, reasonableness)
III. Objections:
   A. Overbreadth and undue burden (scope/time frame)
   B. Lack of particularity (duces tecum requests 3–7)
   C. Privileged/confidential materials (log provided; request in-camera review)
   D. Non-possession/non-control (identify custodian if known)
IV. Requested relief:
   - Narrow to [time window/custodians]
   - Protective order (confidentiality; redactions)
   - Reasonable compliance schedule
V. Prayer

16) Quick FAQ

Do I need a lawyer? It’s strongly advisable, especially if criminal exposure, privilege issues, or corporate data are involved.

Can I refuse entirely? Rarely justified. Courts expect tailored objections and good-faith partial compliance.

What if I truly don’t have the documents? Say so in writing, explain the search conducted, and identify the likely custodian if known.

Can I send electronic copies? Often yes, unless originals or specific formats are required. Confirm accepted formats or propose reasonable ones.

What if I discover more documents after producing? Produce supplements promptly, referencing the earlier transmittal.

17) One-page action plan (pin this)

Validate the subpoena (authority, particulars, scope).
Calendar the deadline; preserve evidence.
Scope & collect; review for privilege and DPA.
Decide: comply, negotiate narrowing, or move to quash/modify.
Execute: appear and testify, or produce with cover letter and log.
Document everything (searches, decisions, productions).

If you’d like, I can adapt the templates to your exact subpoena (redacting sensitive info), or draft a tailored motion to modify/quash based on your grounds.