Philippine succession law can feel confusing because the surviving spouse can receive property in two different ways:

As an owner under the property regime of the marriage (Absolute Community, Conjugal Partnership, etc.), and
As an heir of the deceased (through legitime and/or intestate succession, and possibly through the free portion if there is a will).

A correct computation always separates these two.

1) Start With the Correct “Estate” (Because the Spouse May Already Own Half)

Before you compute inheritance shares, identify what property is actually part of the decedent’s estate.

A. Identify the applicable property regime

Most marriages today commonly fall into:

Absolute Community of Property (ACP) (default for marriages without a valid pre-nuptial agreement)
Conjugal Partnership of Gains (CPG) (common for older marriages, or if specifically applicable)
Separation of Property (if agreed)

B. Liquidate the marital property first (this is not inheritance)

ACP (simplified):

Determine the community property.
Pay community obligations (debts properly chargeable to the community).
Divide what remains 50/50 between spouses.
The deceased’s 50% becomes the base for inheritance distribution (together with any exclusive property of the deceased, if applicable).

CPG (simplified):

Identify exclusive properties of each spouse (generally remain exclusive).
Determine the conjugal gains (net gains during marriage).
Pay conjugal obligations.
Divide net gains 50/50.
The decedent’s estate typically consists of:
- the decedent’s exclusive property, plus
- the decedent’s share in the net conjugal gains.

Key point: The surviving spouse’s half (in ACP/CPG) is not inherited from the decedent—it is the spouse’s own property.

C. Compute the net hereditary estate

From the decedent’s share (after liquidation), deduct:

allowable debts and obligations chargeable to the estate,
expenses as recognized by law,
and account for advances/collation issues where applicable (in broad terms, gifts that must be brought to the mass when required).

What remains is the net hereditary estate—this is what you divide among heirs.

2) Identify the Children (Because Shares Differ)

Philippine law treats children differently depending on status:

A. Legitimate children

Inherit in their own right.
Adopted children generally inherit like legitimate children.

B. Illegitimate children

Have inheritance rights, but their shares are generally smaller in relation to legitimate children in many computations.

C. Representation

If a child of the decedent predeceased, that child’s descendants (grandchildren) may inherit by right of representation, stepping into the predeceased child’s place (especially within the direct descending line).

3) Determine Whether There Is a Will (Testate vs. Intestate)

Two big frameworks:

Testate succession (with a will) You must respect legitimes of compulsory heirs, and only the free portion may be freely disposed.
Intestate succession (no will, or will ineffective) The law sets the shares.

Even with a will, the computation usually still starts by reserving legitimes.

4) The Core Concept: “Legitime” (Minimum Reserved Shares)

Compulsory heirs (relevant here) include:

legitimate children and descendants,
illegitimate children,
surviving spouse.

A will cannot reduce their shares below their legitimes (subject to valid disinheritance, etc.).

A. Legitime of legitimate children (collectively)

Generally: 1/2 of the net hereditary estate is reserved for legitimate children (collectively), divided equally among them.

B. Legitime of the surviving spouse (when children exist)

When legitimate children exist, the spouse’s legitime is equal to the legitime of one legitimate child.
When illegitimate children exist (and no legitimate children), the spouse’s legitime is commonly treated as 1/4 of the estate in the standard legitime scheme used in practice and doctrine.

C. Illegitimate children’s legitime (general rule of thumb)

Commonly treated as 1/2 of what a legitimate child receives, in the typical comparative computation framework.

Because legitime interactions can vary by heir-combination, many lawyers compute using the known statutory patterns and then verify whether there is any free portion left.

5) Intestate Shares (No Will): The Most Used Formulas

When there is no will, or succession becomes intestate, these are the classic spouse-and-children distributions.

Scenario 1: Surviving spouse + legitimate children

Rule of thumb: the spouse gets a share equal to one legitimate child.

If there are N legitimate children, the estate is divided into N + 1 equal parts.

Each legitimate child = 1 / (N + 1)
Surviving spouse = 1 / (N + 1)

Example: Estate = ₱6,000,000; spouse + 3 legitimate children Total shares = 3 + 1 = 4 parts Each child = ₱1,500,000 Spouse = ₱1,500,000

Scenario 2: Surviving spouse + illegitimate children (and no legitimate children)

A commonly applied intestate pattern:

Surviving spouse = 1/3
Illegitimate children (collectively) = 2/3, divided equally among them

If there are M illegitimate children:

Each illegitimate child = (2/3) / M
Spouse = 1/3

Example: Estate = ₱3,000,000; spouse + 2 illegitimate children Spouse = ₱1,000,000 Children’s collective = ₱2,000,000 → ₱1,000,000 each

Scenario 3: Surviving spouse + a mix of legitimate and illegitimate children

This is where people most often make mistakes. A practical way to compute is:

Compute the legitimate child shares under the spouse + legitimate children rule (spouse treated like one legitimate child).
Then allocate illegitimate children in a way consistent with their recognized fraction relative to legitimate children in the governing scheme (often conceptualized as half a legitimate child’s portion), ensuring the resulting distribution fits the applicable rule-set.

Because mixed legitimate/illegitimate computations can become fact-sensitive (especially where there are multiple heirs and potential will provisions), lawyers typically compute this using a standardized “unit” method and then confirm compliance with the Civil Code provisions for the exact heir set.

(If you want a concrete numerical worked example for your specific family composition—number of legitimate children, number of illegitimate children, and whether there is a will—you can compute it cleanly using the step-by-step method in Section 9.)

6) Testate Shares (With a Will): Reserve Legitimes First, Then Apply the Will

With a will, you generally follow this order:

Pay estate obligations (after marital liquidation).
Set aside legitimes of compulsory heirs (spouse + children).
The remainder is the free portion, distributed according to the will.
If the will gives less than legitime to a compulsory heir, it is reduced/adjusted to comply with legitime rules (subject to valid disinheritance).

A. Typical “spouse + legitimate children” testate computation

Let:

Estate = E
Number of legitimate children = N

Legitimate children collectively reserve E/2. Each child’s legitime = (E/2) / N
Spouse’s legitime = equal to one legitimate child’s legitime = (E/2) / N
Free portion = E − [E/2 + (E/2)/N] = E/2 − (E/2)/N

Important effect:

If N = 1 (one legitimate child), spouse legitime equals child legitime = E/2, and total legitimes can consume all of E (leaving no free portion).

7) Don’t Forget These Common “Share-Changers”

A. Predeceased child → representation

If a legitimate child predeceased leaving descendants, those descendants generally take the share the child would have received, divided among them.

B. Renunciation

If an heir validly renounces:

In intestacy, renunciation can alter who takes (including accretion/representation consequences).
In testacy, it can affect who receives the free portion or substituted shares if substitution was provided.

C. Disinheritance

A compulsory heir’s legitime can be lost only through valid disinheritance (must comply with legal formalities and grounds).

D. Advances/collation

Some lifetime gifts may need to be “brought to the mass” for equalization in partition (depending on recipient and nature of transfer). This can change the final distribution even if fractional shares are correct.

8) The Step-by-Step Computation Checklist (The “Do This Every Time” Method)

Step 1 — Identify the property regime

ACP / CPG / Separation.

Step 2 — Liquidate marital property

Compute the surviving spouse’s own share first.

Step 3 — Determine the net hereditary estate (E)

Decedent’s share after liquidation minus estate-chargeable obligations = E

Step 4 — Identify compulsory heirs

Surviving spouse
Children (legitimate, illegitimate, adopted)
Check for representation issues

Step 5 — Decide framework

Intestate? Apply statutory intestate shares.
With will? Reserve legitimes, then apply will to free portion.

Step 6 — Compute fractions, then pesos

Compute the fractional shares first; then multiply by E.

Step 7 — Validate

Total must equal 100% of E.
Legitimes must not be impaired (unless validly disinherited).
Confirm no double-counting of the spouse’s marital share.

9) Fully Worked Examples (Including Marital Liquidation)

Example A: ACP + intestacy + spouse + 2 legitimate children

Facts

Total community property = ₱10,000,000
Community debts = ₱2,000,000
No exclusive property
No will
Heirs: surviving spouse + 2 legitimate children

1) Liquidate ACP Net community = 10,000,000 − 2,000,000 = ₱8,000,000 Spouse owns half = ₱4,000,000 (NOT inheritance) Decedent’s half = ₱4,000,000 → hereditary estate E

2) Intestate shares (spouse + legitimate children) N = 2 legitimate children → divide into N+1 = 3 equal shares Each child = 1/3 of E = ₱1,333,333.33 Spouse inheritance share = 1/3 of E = ₱1,333,333.33

3) Spouse’s total receipt

Spouse marital share: ₱4,000,000
Plus inheritance: ₱1,333,333.33 = ₱5,333,333.33 total (from all sources)

Example B: Separation of property + intestacy + spouse + 3 illegitimate children

Facts

Decedent exclusive property = ₱6,000,000
No marital pool to liquidate
No will
Heirs: spouse + 3 illegitimate children So E = ₱6,000,000

Intestate shares Spouse = 1/3 = ₱2,000,000 Illegitimate children collective = 2/3 = ₱4,000,000 Each illegitimate child = ₱4,000,000 / 3 = ₱1,333,333.33

10) Practical Notes for Real-World Use

A. Always confirm what “estate” you’re dividing

Most family disputes come from forgetting to liquidate ACP/CPG first.

B. Identify every child correctly

Legitimacy status, adoption, and representation issues can change the math.

C. Check whether there is a will—and whether it is effective

Even with a will, legitimes usually control the minimum shares.

D. Taxes and transfer costs are separate from share computation

Estate tax and transfer expenses affect net distributable amounts, but the legal shares are computed from the proper net estate basis used for distribution.

11) Quick Reference Summary

Intestate (no will), spouse + legitimate children

If N legitimate children: each gets 1/(N+1), spouse gets 1/(N+1).

Intestate (no will), spouse + illegitimate children only

Spouse 1/3, illegitimate children collectively 2/3.

With a will (testate)

Reserve legitimes first (children + spouse), then distribute free portion as the will provides.

If you share a specific family composition (number of legitimate children, number of illegitimate children, whether any child predeceased leaving descendants, and whether there’s a will), you can compute the exact fractions cleanly using the checklist and the appropriate scenario rules above.