PCT Chapter I vs Chapter II National Phase Timing

The PCT gives an applicant two procedural routes through the international phase — Chapter I, which ends in national entry under Article 22, and Chapter II, which adds a demand for international preliminary examination under Article 31 before national entry under Article 39 — and for decades the choice between them controlled whether national phase fell due at 20 or 30 months. This page explains what each route actually times, the Rule 54bis deadline that governs when a demand must be filed, and why, since the 2002 harmonization, the demand no longer buys extra national-phase time in most offices.

For a docketing system, the practical question is narrow but easy to get wrong: does the presence or absence of a Chapter II demand change the national-phase entry deadline this engine should emit? The honest modern answer is almost never — but the two routes still generate genuinely different intermediate deadlines that must be tracked. This sits beneath the PCT National Phase Entry Rules framework and complements the office-level split covered in USPTO vs EPO National Phase Entry Differences.

What Each Route Times

Chapter I is the default. If the applicant does nothing beyond the international application and its search, national phase is entered under PCT Article 22, whose amended text sets a 30-month period from the earliest priority date.

Chapter II is elective. The applicant files a demand for international preliminary examination under PCT Article 31, which triggers a substantive examination by the International Preliminary Examining Authority and produces an International Preliminary Report on Patentability (Chapter II). National phase for a Chapter II application is entered under PCT Article 39, which prescribes a period of at least 30 months from priority; some offices, notably the EPO under Rule 159(1) EPC, set 31 months.

Operational Action: Key the national-phase entry deadline off the designated office’s rule record, not off a “demand filed” flag — for a modern application the demand changes what report is on file, not when national phase is due.

The Rule 54bis Demand Deadline

If a client wants Chapter II, the one hard intermediate deadline is when the demand must be filed. PCT Rule 54bis sets it as the later of two dates: three months from the date of transmittal of the international search report and the written opinion, or 22 months from the priority date. Miss it and the right to demand international preliminary examination is lost, even though national phase itself remains available under Chapter I.

Because the deadline is a maximum of two candidate dates, a fixed “22 months” reminder is wrong whenever the search report arrives late — the three-months-from-ISR branch can fall after the 22-month mark. Compute both and take the later:

from datetime import date
from dateutil.relativedelta import relativedelta

def demand_deadline(priority: date, isr_transmittal: date | None) -> date:
    """Rule 54bis: the later of 3 months from ISR/written-opinion transmittal
    or 22 months from the priority date. A late ISR pushes the deadline out."""
    twenty_two_months = priority + relativedelta(months=22)
    if isr_transmittal is None:
        # No ISR transmitted yet: the 22-month branch is the only fixed anchor.
        return twenty_two_months
    three_months_from_isr = isr_transmittal + relativedelta(months=3)
    return max(twenty_two_months, three_months_from_isr)

# Priority 2024-01-10 -> 22-month branch = 2025-11-10.
# ISR transmitted late on 2025-09-15 -> 3-month branch = 2025-12-15 (later, wins).
assert demand_deadline(date(2024, 1, 10), date(2025, 9, 15)) == date(2025, 12, 15)
# ISR on time on 2024-06-01 -> 3-month branch = 2024-09-01 (earlier); 22 mo wins.
assert demand_deadline(date(2024, 1, 10), date(2024, 6, 1)) == date(2025, 11, 10)

Operational Action: Compute the Rule 54bis demand deadline as the later of the two branches and re-arm it whenever the ISR transmittal date arrives from the feed — a demand deadline hardcoded at 22 months is wrong every time the search report is late.

The 2002 Harmonization and Why It Matters to Docketing

Before 1 April 2002, the split was consequential: Chapter I national entry under Article 22 fell due at 20 months, and the only way to reach 30 months was to file a Chapter II demand before the 19-month mark, which extended entry to 30 months under Article 39. Docketing systems of that era genuinely had to branch on whether a demand had been filed.

The 2002 amendment to Article 22(1) raised the Chapter I period to 30 months, aligning it with Article 39. For any application with an international filing date on or after 1 April 2002, the 30-month period applies whether or not a demand was filed. A small number of designated offices whose national law could not be amended in time filed reservations under Article 22, preserving the old 20/30-month split; those reservations have been progressively withdrawn, and the current status is published in the WIPO PCT Contracting States table and reservations notices. Treat that table as version-pinned input, not a constant.

The docketing consequence is a common bug: keying the national-phase window off chapter_ii_demand for a modern application over-counts by a month in the rare reserved office and, more often, simply carries dead logic. The PCT 30/31-Month Deadline Calculators approach is authoritative here — the office rule file decides the window, and the demand flag is metadata about what report exists, not a timing input:

from datetime import date
from dateutil.relativedelta import relativedelta
from dataclasses import dataclass

@dataclass(frozen=True)
class EntryTiming:
    national_phase_deadline: date
    demand_relevant_to_timing: bool  # True only for a reserved legacy office

def national_phase_timing(priority: date, office_months: int,
                          demand_filed: bool, office_reserved_20_30: bool) -> EntryTiming:
    """For a post-2002 application the demand does not move the deadline unless
    the designated office kept an Article 22 reservation."""
    deadline = priority + relativedelta(months=office_months)
    # The demand only affects timing in a legacy reserved office.
    demand_matters = office_reserved_20_30 and not demand_filed
    return EntryTiming(deadline, demand_matters)

# Modern office, 30-month window: demand filed or not, same national-phase date.
assert national_phase_timing(date(2024, 1, 10), 30, True, False).national_phase_deadline == date(2026, 7, 10)
assert national_phase_timing(date(2024, 1, 10), 30, False, False).national_phase_deadline == date(2026, 7, 10)

When the Chapter II Demand Still Matters

Even though the demand rarely changes national-phase timing, it is far from irrelevant, and a docketing model should not discard it:

• The Rule 54bis deadline is real and short. If the client wants an examined IPRP Chapter II, missing the demand deadline forecloses that option irreversibly, so it must be docketed as its own tracked deadline distinct from national entry.
• Article 34 amendments. A demand opens the right to amend the claims, description, and drawings before the examining authority under Article 34, on a schedule tied to the international preliminary examination — deadlines worth surfacing.
• A stronger record for national phase. A favorable IPRP Chapter II can streamline prosecution in several offices, which is a strategic reason to file the demand even without a timing benefit.

The rule the engine enforces is simple: national-phase timing comes from the office rule record; the demand generates its own separate deadline chain. Mapping the international-bureau transmittal triggers that feed both is covered in How to Map PCT Rule 47 Deadlines to National Phase.

Frequently Asked Questions

Related

• PCT National Phase Entry Rules — the engine that resolves the per-office national-phase window.
• USPTO vs EPO National Phase Entry Differences — how the 30/31-month split plays out office by office.
• How to Map PCT Rule 47 Deadlines to National Phase — separating international-bureau transmittal triggers from statutory entry windows.
• PCT 30/31-Month Deadline Calculators — the calculators that emit the window the office rule record selects.

↑ Back to PCT National Phase Entry Rules