Here’s a comprehensive, practice-oriented legal guide—Philippine context—on Collection of Sum of Money suits after sending a demand letter: when to sue, where, how, defenses you’ll face, interest/fees, and how to actually collect once you win. No browsing used.

1) What a “collection of sum of money” case is (and when to file)

A collection suit enforces a debtor’s obligation to pay a determinable amount—typically from a loan, sale of goods/services, promissory note, checks, account stated, or unjust enrichment.

A demand letter is not always a legal prerequisite to sue, but it’s crucial because it:

Puts the debtor in delay (mora) → triggers interest and damages from the date of demand (or from filing if no demand).
Shows good faith and can help you recover attorney’s fees when you’re “compelled to litigate.”
Often satisfies contractual notice clauses.

When to pull the trigger:

The debt is due and demandable, demand was refused/ignored, and informal settlement has failed.
Watch prescription:
- 10 years – upon a written contract, promissory note, or other written obligation.
- 6 years – oral or implied contracts; quasi-contract (e.g., unjust enrichment).
- 4 years – quasi-delict (rare in straight collections).

2) Demand letter: what to include (and why it matters)

Key contents

Parties and debt reference (contract/invoice/check numbers; dates).
Exact amount due (principal + accrued interest/penalties as of a cut-off date), with running interest thereafter.
Legal basis (contract clause, delivery & acceptance, check issued/dishonored).
Firm deadline to pay (e.g., 5–10 days from receipt).
Payment instructions and where to send queries.
Consequences of non-payment (suit; interest; attorney’s fees per contract/law).
Mode of service that’s provable: personal with acknowledgment, registered mail (keep registry receipts/return card), courier with tracking, or email with read receipts.

Good practice: Attach Statement of Account (SOA), invoices, delivery receipts (DRs), and the promissory note or check images. These become your exhibits later.

3) Where and how to file: forums, thresholds, and procedures

A) Small Claims (no lawyers appearing; fast; documentary)

Coverage: Pure money claims without damages (other than interests, costs, attorney’s fees) up to ₱1,000,000 (exclusive of interest/costs).
How: File a Verified Statement of Claim with all supporting documents (contracts, SOA, DRs, ORs, emails, demand letter + proof of receipt).
Process: Court serves Summons; single hearing focused on documents; judgment on the same day where possible.
Finality: No appeal; judgment is immediately final and unappealable (exceptional recourse is a Rule 65 petition for grave abuse—rare).

B) Regular civil action (through counsel)

Jurisdictional amounts (personal actions):
- First-level courts (MTC/MeTC/MTCC) – claims not more than ₱2,000,000, exclusive of interest, damages, attorney’s fees, and costs.
- RTC – exceeds ₱2,000,000.
Venue (personal action): Where the plaintiff or defendant resides (at plaintiff’s option), unless a written venue stipulation exists.
Pleadings: Verified complaint recommended (especially if you want provisional remedies). Attach actionable documents (e.g., contract, note, check, SOA) as annexes; a party relying on a document must attach it and the adverse party must specifically deny under oath if authenticity is questioned.
Timeline (nutshell): Summons → Answer (30 calendar days) → pre-trial & mediation/JDR → trial (documentary, then witnesses) → decision.

C) Barangay conciliation (condition precedent in many cases)

Required before filing when both parties are natural persons residing in the same city/municipality, and no statutory exception applies.
Not required when at least one party is a juridical entity (corporation/partnership), or parties live in different cities/municipalities, or the case falls under recognized exceptions (e.g., with provisional remedy needed).
File your Certificate to File Action (CFA) with the court to show compliance.

4) Legal bases you can plead (choose what fits the facts)

Breach of written contract (loan, sales, services, lease).
Promissory note/loan acknowledgment.
Open account / account stated (debtor failed to dispute periodic statements within a reasonable time; silence = implied assent).
Dishonored checks (civil liability for the amount + interest/fees; BP 22 is separate criminal liability you may pursue in parallel, but not required).
Quantum meruit / unjust enrichment (you delivered value, debtor benefited without paying; useful when formal contract is lacking).
Surety/guaranty (proceed directly against a surety; for a guarantor, observe benefit of excussion rules unless waived).

5) Interest, penalties, attorney’s fees, and how courts compute

Conventional interest: Enforce per contract if clearly stipulated (rate + basis). Unconscionable penalty charges may be reduced by the court.
Legal interest: If no valid stipulation, 6% per annum (simple) generally applies—
- Loans/sum certain: from demand (or from filing of complaint if no demand).
- Judgments: 6% per annum from finality of judgment until fully paid.
Attorney’s fees: Recoverable by stipulation or when the prevailing party was forced to litigate; still discretionary and must be reasonable (courts often award a percentage or fixed sum supported by proof).
Liquidated damages/penalties: Enforceable if not iniquitous; courts may moderate them.

Always plead the dates of default and show your math in an annex (interest table). Courts appreciate transparent computations.

6) Provisional and post-judgment remedies (to actually collect)

A) Before judgment

Preliminary attachment (Rule 57): If the debtor is about to abscond, fraudulently disposing of property, or the claim is based on embezzlement/willful breach, etc. Requires:
- Verified application stating a statutory ground,
- Attachment bond, and
- A claim for a specific sum. The sheriff can attach real or personal property, which later secures satisfaction.

B) After judgment (Rule 39 execution)

Garnish bank accounts, receivables, or salaries (serve writ on garnishee).
Levy on personal then real property (sheriff’s sale).
Examination of judgment obligor and third parties (to discover assets).
Receivership/charging orders (for partnership interests), if apt.
Contempt for disobedience to orders (e.g., refusal to turn over assets already garnished).

7) Evidence that wins collection cases

Contracts/notes (signed), ORs/ARs, invoices, delivery receipts (with signatures), job orders, service completion certificates, email chains acknowledging debt, SOAs and debtor’s partial payments (killer evidence), checks/deposit slips, demand letter + proof of receipt.
For account stated: show regular SOAs + no timely written objection + subsequent payments.
For services: show scope of work, time sheets, acceptance emails, project sign-offs.

Authenticate your exhibits (who issued them, how kept, and who can testify). For corporate plaintiffs, designate a records custodian witness.

8) Common defenses (and how to anticipate them)

Payment/set-off/condonation – rebut with receipts and bank proof.
No delivery / defective goods or services – answer with DRs, acceptance notes, warranty logs; show debtor’s use/benefit.
Forgery / lack of authority – if a corporate debtor claims the signer lacked authority, respond with ratification/acceptance by the corporation, course of dealing, and benefit received.
Usury/unconscionable interest/penalties – be ready to defend the rate’s reasonableness; offer alternative computation at legal interest.
Prescription – compute carefully from due date/last payment/last written acknowledgment (acknowledgment can restart prescription).
Improper venue / no barangay conciliation – cure by filing in the proper venue and/or showing an exception or CFA.

9) Special tracks

A. Checks (BP 22 overlaps)

You may file criminal BP 22 separately or simultaneously with the civil case. Criminal proof of issuance and dishonor helps settlement leverage; civil case secures actual recovery. Keep bank return memos (“DAIF”, “Account Closed”) and notice of dishonor attempts.

B. Security interests

If you hold chattel or real estate security, consider foreclosure in parallel with or instead of a pure collection suit (watch anti-forum shopping; craft pleadings carefully).

C. Guaranty vs. Surety

Surety is solidary—you can sue the surety directly.
Guarantor generally enjoys excussion—go after principal debtor’s assets first, unless waived.

10) Litigation roadmaps (concise)

Plaintiff (standard collection)

Final demand (with computation & deadline) → keep proof of service.
Check prescription, venue, barangay conciliation need.
Choose Small Claims (≤ ₱1M, documentary) or Regular action.
Prepare complaint/SOC with all exhibits; consider attachment if risk of asset flight.
Pre-trial: mark exhibits; push stipulations (debt, deliveries, interest clause).
Trial (if any): lead with custodian of records + accounting witness.
Judgment → Writ of Execution → garnish/levy.
Post-judgment interest until satisfaction.

Defendant (if you receive a demand/summons)

Audit the claim: compute your exposure; gather proof of payment/defects.
Negotiate (discount for lump-sum/short plan).
If sued: file Answer in 30 calendar days (regular cases) or Response per small claims rules; assert counterclaims/set-off with documents.
Consider consignation (deposit what’s due in court) to stop interest if there’s a bona fide dispute on small balance or payee.

11) Templates you can reuse (short forms)

A) Final Demand (essential paragraphs)

We refer to your obligation under [contract/ref] for ₱[principal], due [date]. Despite prior reminders, the account remains unpaid. As of [cut-off date], your total due is ₱[principal + accrued interest/penalties]. Thereafter, interest accrues at [x%/yr or 6%/yr legal rate] until full payment. Kindly pay within [5/10] days from receipt to avoid legal action, additional costs, and attorney’s fees. Please direct payment to [bank details] and email [address] with proof.

B) Interest Computation Sheet (attach to demand/complaint)

Principal: ₱____
Contract rate: __% p.a. (or 6% p.a. legal interest)
Accrual start: [date of default/demand]
Days/years elapsed: ___
Interest to [cut-off]: ₱____
Running interest: ₱____ /day from [cut-off] until paid.

12) Practical tips that move the needle

Paper is king: Courts decide collections on documents. If it’s not attached, it almost doesn’t exist.
Make the debtor talk: Written acknowledgments or partial payments are powerful—they interrupt prescription and prove liability.
Mind your math: Provide clear, conservative computations; offer an alternative using legal interest if the court finds your penalty unconscionable.
Think like an enforcer: Identify attachable assets before filing (banks, receivables, vehicles, realty).
Settlement windows: Pre-trial and just before execution are prime moments—have tiered offers ready.

13) Bottom line

After a proper demand, a collection of sum of money suit turns on clean documents, correct forum, and credible computations.
Choose Small Claims (≤ ₱1M) for speed, or a regular action (MTC ≤ ₱2M; RTC > ₱2M) when amounts are higher or issues are complex.
Use attachment if there’s asset flight risk; lock in interest and fees by pleading and proving them right.
Winning on paper is half the battle; plan execution from day one so your judgment turns into cash.

This is general information, not legal advice. For live matters (e.g., cross-claims, secured debts, or multiple defendants), consult counsel to tailor pleadings, remedies, and execution strategy to your facts and venues.