Below is a structured legal-style article covering the essentials.

I. Legal Nature of Erroneous Proceeds

A. Solutio Indebiti (Payment by Mistake)

Under the Civil Code, solutio indebiti arises when:

A person receives something not due to them, and
The delivery/transfer was made through mistake.

Articles 2154–2155 of the Civil Code (on quasi-contracts) provide that the recipient is obliged to return what was received by mistake. Relatedly, Article 22 (unjust enrichment) prohibits one person from unjustly enriching themselves at the expense of another.

Applied to bank errors:

If your account is credited with funds that are not yours (e.g., misposting, duplication, wrong account number), you are legally bound to return those funds.
If you already used the money, you are generally obliged to restitute what you received, possibly with interest or damages depending on the circumstances.

B. Distinguishing Sources of Erroneous Proceeds

Bank Error
- The bank accidentally credits your account (e.g., double posting, wrong account mapping).
- The bank (or depositor affected) has a claim for restitution based on solutio indebiti and unjust enrichment.
Sender Error (Wrong Transfer)
- An individual/company transfers money to your account by mistake (wrong account number, typo in mobile number, etc.).
- The sender has a claim to demand the return of the funds; the bank becomes involved as intermediary and custodian of the account.
Fraud or Scam Proceeds
- Proceeds of crime accidentally routed to your account.
- In addition to civil obligations, there may be AMLA and criminal law consequences if you conceal or use the funds.

II. Obligations of the Recipient

A. Duty to Inform and to Return

Once you become aware that the funds are not yours, you are expected to:

Notify the bank immediately
- This demonstrates good faith.
- It is usually done via written/email complaint or branch visit.
Refrain from using the funds
- Continuing to withdraw, transfer, or spend the money, despite knowing it is not yours, may be interpreted as bad faith and can raise criminal exposure.
Cooperate in return of the funds
- You may sign authorization forms, acknowledgment letters, or reversal instructions.

Failing to return money you know you are not entitled to can lead to:

Civil liability for unjust enrichment and damages.
Possible criminal liability, often under estafa provisions of the Revised Penal Code (e.g., misappropriation of money belonging to another).

III. Obligations and Powers of the Bank

A. Power to Correct Erroneous Entries

Banks generally have the right, and in fact the duty, to correct erroneous postings in their books. In practice, they may:

Reverse the erroneous credit from your account once the error is confirmed, sometimes without your prior consent, especially if:
- The error is clearly internal; and
- You have not yet withdrawn or used the funds.

Courts have recognized that a bank is not required to honor the customer’s “right to retain” money that is undisputedly not due to them, provided due process and prudence are observed.

B. Due Diligence and Consumer Protection

Banks are regulated institutions and must adhere to:

Know-Your-Client (KYC) and transaction monitoring under AMLA.
Disclosure and fair dealing obligations under financial consumer protection rules.
Complaint handling standards set by Bangko Sentral ng Pilipinas (BSP).

Accordingly, once you inform the bank that a credit is erroneous and ask for guidance on returning the funds, the bank is expected to:

Acknowledge the concern (at least via email/SMS/branch receipt).
Investigate the transaction (source, nature of credit, possible fraud).
Provide instructions on how the funds will be reversed or refunded.
Document the reversal/refund with clear records.

If the bank simply ignores you—no acknowledgment, no guidance, no action—this may constitute a violation of their internal complaint procedures and financial consumer protection standards.

IV. When the Bank Ignores Your Request to Return Erroneous Proceeds

A. Typical Scenarios

You receive an unexpected credit (e.g., ₱50,000) from an unknown source, and:
- You immediately report it via hotline and branch; or
- You send written requests asking the bank to revert or contact the sender.
The bank does not respond or merely gives generic answers like “just ignore it” or “we will investigate” but no concrete action is taken for a long time.
Later, the sender or law enforcement contacts you demanding the full return of the funds, possibly accusing you of misappropriation, even though you tried to return the money early on.

In this context, your concern is both legal risk management and forcing the bank to act.

V. Legal Risks if You Do Nothing

Even if the bank is silent, you do not acquire ownership of the erroneous proceeds.

Risks include:

Civil Case
- The true owner (sender) or the bank can file a civil action for restitution plus interest and damages.
- Your early written efforts to return the funds help show good faith and may reduce liability.
Criminal Case (Estafa / Related Offenses)
- If you knowingly retain and use the money, it can be construed as misappropriation of funds received by mistake.
- Your recorded attempts to return the proceeds (emails, letters, complaint reference numbers) may be crucial in defending yourself.
Account Freezing or Closure
- The bank may later freeze your account or restrict transactions if an investigation is opened, especially if AML/fraud issues are suspected.
- They may also close the account with proper notice.

VI. Step-by-Step: How to Escalate When the Bank Ignores You

Step 1: Document Everything

Immediately create a paper trail:

Account statement / screenshots showing the erroneous credit.
Copies of emails, letters, or chat logs where you:
- Inform the bank of the mistake.
- Explicitly offer to return the funds.
Branch visit records:
- Request the branch to stamp-receive your written letter.
- Note the names of officers you speak with and the date/time.

This documentation is your primary defense and a key requirement when escalating to regulators.

Step 2: Send a Formal Written Demand to the Bank

Prepare a formal letter (or email) addressed to the bank’s Branch Manager and Customer Care / Head Office, stating:

Facts:
- Date and amount of erroneous credit.
- Reference numbers, transaction IDs, and account details.
Your Position:
- You acknowledge that the funds are not yours (or at least that they appear erroneous).
- You are willing, ready, and able to return the funds.
Requests:
- That the bank immediately coordinate with the actual owner and effect the reversal.
- That they provide written confirmation of how the funds will be handled.
Warning:
- You are sending this to avoid any allegation of bad faith and to comply with your obligations under civil law.

Give a reasonable deadline (e.g., 10–15 banking days) for the bank to respond in writing.

Step 3: Use the Bank’s Internal Complaint Mechanism

Most banks have a defined complaint/feedback channel:

Hotline / customer care email
Web form or app-based complaint
Branch complaint log / forms

When filing, ensure:

You get a reference number or case ID.
You ask for a written response (email or letter).
You retain screenshots of the complaint submission.

This is important because regulators generally expect that you exhaust internal remedies first before escalating.

Step 4: Escalate to Bangko Sentral ng Pilipinas (BSP)

If the bank still ignores you or gives inadequate responses, escalate to the BSP consumer protection unit (financial consumer protection). In your complaint:

Identify the bank, branch (if applicable), and your account (mask some digits for security).
Attach:
- Copies of account statements/screencaps of the erroneous credit.
- Copies of all letters/emails sent to the bank.
- Proof that the bank received your complaints (reference numbers, stamped receipts).
Explain clearly:
- That you received funds not belonging to you.
- That you promptly requested guidance and offered to return/refund.
- That the bank has been non-responsive or unhelpful, exposing you to legal risk.

Regulators can:

Direct the bank to formally address your issue.
Monitor if the bank’s complaint handling complies with consumer protection rules.
In some cases, facilitate a mediation-style resolution.

Step 5: Consider a Lawyer’s Letter

If the amount is significant or there is already threat of litigation or criminal complaint, consider:

Engaging a Philippine lawyer to send a demand or clarification letter to:
- The bank, and/or
- The sender (if known).

The letter can:

Emphasize your early attempts to return the funds.
Demand that any claim against you consider your good faith cooperation.
Warn that failure of the bank to act may itself cause you damage, for which you may seek relief.

Step 6: Prepare for Possible Civil or Criminal Proceedings

If the true owner or law enforcement appears:

Show your complete documentation:
- Early notices to the bank,
- Explicit offers to return,
- Any attempts to segregate or hold the funds untouched.
If there is a subpoena or complaint, consult a lawyer immediately to frame your response and assert your good faith.

VII. Special Situations

A. You Already Used Part or All of the Funds

If you honestly did not know the credit was erroneous (e.g., you thought it was a legitimate payment or refund), but later learned it was an error:

You are still liable to return what was not due.
Courts may consider:
- Your good faith at the time of spending, and
- Your subsequent willingness to make restitution (e.g., installment payments, partial refunds).

The sooner you openly disclose and offer to settle, the better.

B. The Bank Later Reverses Without Notice

Sometimes banks correct the error by debiting the amount from your account after investigation, with minimal or late notice, which may:

Cause bounced checks, failed automatic debits, or negative balances.
Lead to penalties or reputational issues for you.

You may then have a separate claim for damages against the bank if:

They acted without proper notice or timing; and
Their manner of correction was unreasonable or contrary to their duties of prudence and good faith as a bank.

C. Fraud / Scam Involving Third Parties

If the erroneous funds are tied to:

Online scams, phishing, or unauthorized transfers, or
Law enforcement affidavits or freeze orders,

Then additional laws come into play (e.g., AMLA, Cybercrime Prevention Act). In such cases:

Cooperate with law enforcement directives.
Coordinate with the bank but avoid making statements without legal advice, as these may be used in investigations.

VIII. Evidentiary Considerations

In any dispute, these documents and facts will be crucial:

Timing
- When you received the money vs. when you first notified the bank.
Communications
- Written letters, emails, chat logs, complaint reference numbers.
Actions on the Account
- Whether you used or moved the funds after knowing they were not yours.
Bank Response or Non-Response
- Delays, generic replies, failure to give instructions or acknowledgments.

A person who immediately notifies the bank and refrains from using the funds is in a much stronger legal position than one who stays silent and continues to spend.

IX. Practical Do’s and Don’ts for Consumers

Do:

Notify the bank in writing as soon as you suspect an erroneous credit.
Keep the funds untouched until the issue is resolved, or at least set them aside.
Maintain a complete file of all communications and account statements.
Use the bank’s official complaint channels and get reference numbers.
Escalate to BSP if the bank remains non-responsive.

Don’t:

Assume you can keep the money just because the bank is silent.
Spend, transfer, or conceal the funds once you suspect error.
Rely solely on verbal assurances from bank staff; always seek written confirmation.
Ignore letters or demands from the sender or law enforcement.

X. Conclusion

In Philippine law, erroneous proceeds never truly become yours; they are subject to return under solutio indebiti and unjust enrichment rules, and your handling of them can trigger civil and criminal consequences.

When a bank ignores your request to return such funds, the safest course is to:

Create a clear documentary trail showing your good faith and willingness to return;
Persistently use and exhaust internal channels of the bank;
Escalate to BSP and, when appropriate, consult a lawyer for tailored advice.

This dual approach—legal compliance + regulatory escalation—both protects you personally from liability and presses the bank to fulfill its duties as a regulated financial institution.