What is an ACH routing number and why it matters for US payments

What are ACH payments, and how do they benefit businesses?

Before understanding ACH routing numbers, you need to know what ACH payments are and why they matter to your business operations.

ACH stands for Automated Clearing House, a US-based electronic payment network that processes batch transactions between bank accounts. Think of it as the American equivalent of Singapore's FAST or PayNow systems, but designed for the US banking system.

Purpose and format of ACH payments

The ACH network, administered by the NACHA (National Automated Clearing House Association), was built to move money electronically without the cost and delays of paper cheques or the high fees of wire transfers. Each transaction follows a standardised format that includes specific data elements:

• Standard Entry Class (SEC) codes: Three-character codes that define the transaction type and rules that apply
  
• Routing transit number: The nine-digit routing number identifying the financial institution
  
• Account number: The recipient's specific account within that bank
  
• Transaction amount: The exact dollar value being transferred
  
• Effective entry date: When the funds should be available to the recipient
  

Common SEC codes you will encounter:

• PPD (Prearranged Payment and Deposit): Used for direct deposit of payroll, pensions, and recurring payments to individuals
  
• CCD (Cash Concentration or Disbursement): Designed for business-to-business transactions between corporate accounts
  
• WEB: For internet-initiated payments like online bill pay or e-commerce purchases
  
• CTX (Corporate Trade Exchange): Supports detailed remittance information for vendor payments, including invoice numbers and payment details
  

Variations in ACH payment types

Not all ACH transactions work the same way. Understanding the difference between ACH credit and ACH debit helps you choose the right approach for your business needs.

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For Singapore small businesses and startups dealing with US partners, ACH credit is typically more relevant, i.e. you're pushing payments to US contractors, suppliers, or employees rather than collecting from US consumers.

Why the ACH Network matters to your business

The ACH network processed over 8.8 billion payments in the third quarter of 2025, demonstrating how fundamental it is to US commerce. For Singapore-based professional services firms, e-commerce businesses, and tech startups dealing with US partners, this network is often unavoidable.

The ACH network handles several transaction types crucial to cross-border business:

• Direct deposit of employee salaries and contractor payments
  
• Automatic bill payments and vendor invoices
  
• Business-to-business payments
  
• Tax payments and refunds
  
• E-commerce transactions
  

How the ACH Network works: Basics of ACH transfers

Understanding how ACH transactions flow helps you avoid common mistakes that cause payment failures. The process involves multiple parties and happens in carefully orchestrated steps.

The ACH payment journey

When you initiate an ACH payment, here's what happens behind the scenes:

• Payment setup: You enter the recipient’s routing number and account number through your bank or payment platform.
  
• Batch processing: Your bank groups your payment with others instead of processing it instantly. This batching keeps ACH costs low.
  
• Network routing: Batches are sent several times a day to the ACH network, which sorts and forwards them to the correct bank.
  
• Settlement: The recipient’s bank verifies the details and credits or debits the account.
  
• Completion: Both sides see the transaction in their accounts. Most ACH payments settle within 1–2 business days.
  

Why ACH takes 1–2 business days

This batch processing is why ACH transfers take longer than instant methods like wire transfers. However, it's also why ACH costs significantly less, usually under USD $1 per transaction, versus USD $25–40 for domestic wires or USD $40–60 for international wires.

For routine payments where timing is predictable (monthly payroll, quarterly vendor invoices, subscription renewals), the 1–2 day settlement window is rarely a problem. You simply initiate payments 2–3 business days before they're due.

Same Day ACH option: When you need faster processing, Same Day ACH is available. Payments submitted before designated cutoff times (typically 10:45 a.m. and 2:45 p.m. EST) settle the same business day. This costs slightly more but still far less than wires, typically USD $1–5 versus USD $25–60.

Same Day ACH limitations:

• Maximum transaction amount: USD $1 million
  
• Must use specific ACH transaction types (not available for all SEC codes)
  
• Both banks must support Same Day ACH (most major US banks do)
  

Common pitfall for Singapore-based finance teams:

ACH operates on US business hours, not Singapore time. This time zone misalignment is often one of the most common causes of unexpected ACH delays.

For example, if you initiate an ACH payment at 10:00 a.m. SGT, it is 9:00 p.m. EST in New York, meaning your payment won't enter the ACH batch until the next US business morning. To avoid this risk, you can schedule ACH payments at least one US business day earlier than you think you need, especially for payroll or contractor payments with fixed deadlines.

Why ACH routing numbers matter

Your ACH routing number ensures payments reach the right destination. Without the correct routing number, your money goes nowhere, or worse, goes to the wrong place. Understanding these risks helps you avoid costly mistakes.

What happens when you use the wrong routing number

Here's the reality of payment failures:

• Immediate rejection: Invalid routing numbers may be rejected before entering the ACH network. Funds stay in your account, but you lose 1–2 business days.
  
• Delayed returns: If a payment enters the network with a retired or incorrect routing number, it bounces back after 4–9 business days, leaving vendors unpaid and confused.
  
• Unavoidable fees: Failed ACH payments still incur fees (typically USD $0.50–3.00 per attempt). One wrong saved routing number can quietly add up over time.
  
• Operational disruption: Late payments can delay services, interrupt supply chains, and strain vendor relationships.
  
• Lost revenue: Providing incorrect ACH details can cause customers to abandon payments, especially for subscriptions.
  
• Compliance risk: Repeated failures may trigger bank reviews or account restrictions.
  

Understanding ACH return codes

When an ACH payment fails, it doesn't simply “fail”; it's returned with a specific ACH return code that explains why.

Common return codes include:

• R01: Insufficient Funds: The sender’s account did not have enough balance at the time of processing.
  
• R03: No Account / Unable to Locate Account: The account number is invalid or does not exist at the receiving bank.
  
• R04: Invalid Account Number: The account number format is incorrect.
  
• R29: Corporate Customer Advises Not Authorised: The recipient has blocked ACH debits.
  

Understanding return codes helps finance teams diagnose issues faster, communicate clearly with vendors or employees, and avoid repeated payment failures.

Why do routing numbers change

According to the National Automated Clearing House Association (NACHA), outdated routing information presents a significant risk to parties originating ACH payments, impacting the ability to collect or disburse payments and affecting customer satisfaction.

Financial institutions add or retire hundreds of routing numbers each year due to:

• Bank mergers and acquisitions
  
• Charter changes or restructuring
  
• Regional consolidation
  
• Branch closures or relocations
  

Real-world example: When Bank A merges with Bank B, accounts at Bank A might be migrated to Bank B's routing numbers. If you're still using Bank A's old routing number 6 months later, your payments fail, even though your vendor's account technically still exists, just under a new identifier.

How to protect yourself

• Verify every new setup: Confirm routing numbers directly with the vendor or bank. Don’t rely on old details.
  
• Audit regularly: Review saved payment templates quarterly, especially after bank mergers.
  
• Use the ABA database: Check routing numbers using the official ABA lookup tool.
  
• Enable validation checks: Use payment processor tools that auto-validate routing numbers before processing.
  

ACH fraud prevention

ACH routing numbers are public identifiers used to direct payments to the correct bank, while account numbers must remain private. Fraud typically occurs when account details are exposed, not because routing numbers are known.

To protect US accounts used for ACH payments, businesses can implement:

• ACH blocks: Prevent unauthorised ACH debits entirely unless explicitly approved.
  
• ACH filters: Allow ACH transactions only from approved counterparties or transaction types.
  
• ACH Positive Pay: Require banks to verify ACH transactions against pre-approved rules before processing.
  

These controls are especially important for Singapore businesses using US accounts through fintech providers, where ACH access is essential but exposure must be managed carefully.

Can Singapore businesses use ACH?

Here's the reality for Singapore-based businesses: ACH is a domestic US payment network. You cannot connect directly to it from a Singapore bank account. However, this doesn't mean ACH is off-limits; you just need the right setup.

What works for Singapore businesses

• USD accounts with US routing details: Use fintech providers that offer US-based business accounts with local routing and account numbers. This gives you ACH access without a US entity.
  
• Common provider types:
  

• Multi-currency fintech business accounts
  
• Payment processors with US banking partners
  
• Virtual US bank accounts via global platforms
  

• ACH credit payments: Send ACH payments to US vendors, contractors, and suppliers using their routing and account numbers.
  
• Receiving ACH payments: Accept ACH from US customers and platforms by sharing your US account details, avoiding international wire fees.
  
• Same Day ACH: Use same-day settlement for urgent payments (up to USD $1 million) if supported by both banks.
  

What doesn't work for Singapore business

• Direct ACH from SGD accounts: ACH cannot be initiated from Singapore bank accounts. It only works with USD accounts at US banks.
  
• ACH debit without US setup: Singapore businesses can’t pull funds from US accounts without proper authorisation and compliance. ACH credit covers most needs.
  
• Limited ACH support: Some providers allow ACH receive-only or send-only. Always confirm full ACH capabilities upfront.
  
• True international transfers: ACH is a US domestic system. It doesn’t replace SWIFT for Singapore–US transfers.
  

Practical setup for Singapore solopreneurs and startups

For Singapore-based startups and SMEs, the practical approach is working with a multi-currency platform that provides US bank account details. This lets you:

• Receive your US routing number and account number upon account approval
  
• Pay US contractors and vendors at local ACH rates (under USD 1 per transaction)
  
• Receive payments from US clients without forcing them to pay expensive international wire fees
  
• Hold funds in USD for future US payments, avoiding unnecessary currency conversions
  
• Access Same Day ACH for urgent transfers
  

This infrastructure eliminates the traditional barriers to cross-border electronic payments without requiring you to establish a US entity or navigate US banking regulations directly.

Pros and cons of using ACH payment services

1. Lower Transaction Costs

ACH payments typically cost far less than credit card payments, wire transfers, or paper-based methods, especially for recurring or high-volume transactions.

To see how this difference impacts your bottom line, consider a simple example.

Imagine your business pays 20 US-based contractors each month. Here’s how the transfer costs compare:

• Wire transfer cost: 20 × USD $35 = USD $700 per month
  
• ACH payment cost: 20 × USD $0.50 = USD $10 per month
  

That’s a monthly cost difference of USD $690, which adds up to USD $8,280 in annual savings.

For businesses making regular US payments, ACH can significantly reduce operating costs compared to wire transfers without sacrificing reliability.

2. Automation & Operational Efficiency

ACH and similar bank transfer services let you automate payments, reducing manual work, errors, and administrative overhead.

3. Better Security vs Paper Checks

Electronic bank transfers replace checks and cash, reducing risks like lost/stolen checks or physical handling errors.

4. Reliable and Traceable Payments

ACH-style transfers leave clear electronic records and often integrate cleanly with accounting systems.

5. Customer/Client Experience

For businesses collecting payments (e.g., subscriptions), these bank-to-bank transfers can improve retention since bank details rarely change compared to credit card numbers.

Cons of using ACH-style payment services

1. Slower settlement times

Traditional ACH transfers settle in 1–3 business days, which may be slower than instant card or FAST payments.

2. Limited real-time capability

Unlike Singapore’s FAST or PayNow real-time systems, classic ACH doesn’t settle instantly, which can affect cash planning.

3. Transaction limits & fees in some cases

Though generally low-cost, ACH transfers can still have per-transaction fees and sometimes limits imposed by banks.

4. International transfer challenges

Standard ACH originated in the US; international ACH or cross-border transfers may involve:

• Slower settlement than local transfers.
  
• Higher fees and foreign exchange costs.
  

Many Singapore businesses instead use local cross-border payment systems or fintech platforms for global transactions.

5. Reversals & Dispute Risks

ACH payments can sometimes be reversed due to errors or disputes, which adds risk for the receiving business.

What are ACH routing numbers used for?

Your ACH routing number acts like a postal code for the banking system; it ensures money reaches the right financial institution. Understanding when and how you'll use these numbers helps you prepare for common business scenarios.

How to accept ACH debits as a business

If you're selling products or services to US customers, accepting ACH debit transactions lets them authorise you to pull payment directly from their bank accounts. This works particularly well for Singapore-based SaaS companies, subscription services, or consulting firms with recurring US revenue.

What you need to set up:

• Your US bank account: A USD business account with US routing and account numbers (typically obtained through a fintech provider if you're Singapore-based)
  
• Customer authorisation: Written or electronic consent allowing you to debit their account; this is legally required under Nacha Operating Rules
  
• Payment processor: Access to an ACH payment gateway that can handle debit transactions
  
• Customer's banking details: Their bank's routing number and account number
  

The customer's routing number tells the ACH network which financial institution to pull funds from. Your routing number identifies where those funds should land.

Critical compliance requirement: You must maintain records of customer authorisation for ACH debit transactions. Without proper documentation, disputes can result in payment reversals and penalties.

How to accept ACH credit transfers as a business

ACH credit transactions are simpler and more common for Singapore businesses; the payer pushes money to you, rather than you pulling it from them. This is the standard method when US clients or platforms pay you for services or products.

To receive ACH credit transfers:

• Provide clients with your routing number and account number
  
• Ensure these details are current and match your bank's records exactly
  
• Monitor incoming payments and reconcile them against invoices
  
• Communicate any changes to your banking details promptly to avoid payment failures
  

For Singapore startups invoicing US clients or e-commerce businesses receiving marketplace payments, ACH credit is often the preferred method.

How to find an ACH routing number?

Finding the correct routing number is crucial for avoiding failed transactions. Here are four reliable methods, ranked from fastest to most thorough.

Using your chequebook

If you have a US bank account with cheques, your routing number appears at the bottom left of every cheque.

The string of numbers follows this format:

• First 9 digits: Your routing number
  
• Next 10–12 digits: Your account number
  
• Final 4 digits: Cheque number
  

Important caveat: The routing number on your cheque might be different from your ACH routing number. Always verify with your bank if you're unsure, especially before setting up automatic payments or payroll.

Using your online or mobile bank account

Most banks display routing numbers in their online banking systems or mobile apps. This is typically the fastest and most reliable method for finding your ACH routing number.

Where to look:

• Log in to your online bank account or mobile app
  
• Navigate to "Account Details," "Account Information," or "Account Settings"
  
• Look for labels like:
  

• "ACH routing number"
  
• "Electronic routing number"
  
• "Routing/transit number"
  
• "Electronic ABA routing number"
  
• "Routing number for direct deposit"
  

The terminology varies by financial institution, but the number itself is always nine digits with no spaces or dashes.

Using the internet

Major banks publish their routing numbers online, and there are official databases you can search. However, this method requires careful attention to detail; many large banks have multiple routing numbers based on state or account type.

The official ABA routing number database lets you search by bank name or routing number.

Contacting customer service

When in doubt, call your bank's customer service line. When calling, specifically ask for: "What is my ACH routing number for electronic payments?"

However, be ready to verify your identity with:

• Account number
  
• ID details
  
• Recent transactions
  
• Business tax ID (if applicable)
  

Customer service can confirm the correct routing number and help you avoid failed payments.

ACH vs ABA routing numbers: The differences

The terms ACH routing number and ABA routing number are often used interchangeably, which creates confusion, especially for international businesses.

An ABA routing number is the original nine-digit bank identifier. An ACH routing number is the same identifier when used specifically for ACH electronic transfers.

In simple terms, all ACH routing numbers are ABA routing numbers, but not all ABA routing numbers work for ACH.

ACH vs ABA routing numbers: History

ABA routing numbers were introduced in 1910 by the American Bankers Association to process paper cheques.

As banking became electronic, the same nine-digit system was reused for:

• Cheques
  
• ACH transfers
  
• Wire transfers (Fedwire)
  

Over time, some banks assigned different routing numbers to each payment type.

ACH vs ABA routing number: Numerical differences

Some banks use one routing number for cheques, ACH, and wires. In these cases, the distinction doesn’t matter.

Larger banks often use separate routing numbers for:

• Cheques
  
• ACH electronic payments
  
• Wire transfers
  
• Different US states
  

Using the wrong one causes payment failure.

How to ensure you have the correct number

Ask banks and vendors one clear question: “What is the ACH routing number for electronic payments?”

• For vendors, always request the ACH routing number, not just “routing number.”
  
• For your own account, check sections labeled Direct Deposit or Electronic Payments in online banking.
  

If numbers conflict, trust bank-confirmed details over cheques or old documents.

Payment method comparison: ACH vs wire vs SWIFT

Choosing the right payment rail affects your costs, speed, and operational efficiency. Not every method suits every situation, and understanding the trade-offs helps you optimise your payment operations.

Comprehensive comparison table

Here's how ACH stacks up against other common methods for international business payments:

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When to use ACH, wire transfer and SWIFT

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Use ACH for routine US payments, wires for urgent or high-value transfers, and SWIFT for international, multi-currency payments.

Strategic approach for Singapore businesses

The optimal strategy for most Singapore businesses operating in US markets:

• Default to ACH for all recurring, predictable US payments under USD 100,000
  
• Use Same Day ACH when you need faster settlement but don't want wire transfer costs
  
• Reserve wires for genuinely urgent situations, very large transactions, or recipient requirements
  
• Use SWIFT for non-US payments or multi-currency needs
  
• Batch ACH payments weekly or monthly to maximise efficiency and minimise administrative overhead
  

This approach balances cost efficiency with operational flexibility, ensuring you're not overpaying for speed you don't need while maintaining the ability to expedite critical payments when necessary.

ACH routing number comparison: Major financial institutions

Understanding how different banks structure their routing numbers helps you avoid common mistakes. Here's a reference for major US financial institutions that Singapore businesses commonly encounter when dealing with US partners.

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Routing numbers are provided for illustration only and may change based on account location, bank mergers, or payment type. Always verify directly with the bank.

Important notes about this table

• Large banks use different routing numbers by state. Your routing number is based on where the account was opened.
  
• Moving states doesn’t change your routing number if the account origin stays the same.
  
• Some banks use separate routing numbers for ACH, wires, and cheques. Always ask for the ACH routing number.
  
• Some banks (e.g., HSBC) use a single ACH routing number nationwide.
  
• Bank mergers can alter routing numbers. Always re-verify after an acquisition.
  

How a fintech platform helps Singapore businesses deal with USD/cross-border payments

Singapore SMEs and startups face a common challenge: accessing US payment networks without the complexity of establishing a US entity or navigating US banking regulations. Traditional solutions required extensive paperwork, physical US presence, or accepting high costs for international wires.

Modern fintech platforms, like Aspire, eliminate these barriers, giving you direct access to the ACH network through US bank account infrastructure built specifically for cross-border businesses.

What Aspire provides for ACH access

• US-based USD accounts with local routing numbers: Get real US bank details with local routing numbers. Send and receive ACH payments like a US business—no wire fees or delays for your payers.
  
• Multi-currency accounts in 30+ currencies: Hold and pay in USD, SGD, GBP, EUR, and 30+ currencies from a single platform with transparent FX.
  
• Faster, cheaper cross-border payments: ACH settles in 1–2 business days at under USD $1 per payment. Same Day ACH available when timing matters.
  
• Built for business operations: All transactions in one dashboard with accounting integrations (Xero, QuickBooks) for automatic reconciliation.
  
• Compliance handled for you: US banking compliance and AML checks are handled for you, reducing operational risk.
  
• Complete payment infrastructure: Accept cards and local payment methods, issue corporate cards, and manage expenses from one platform.
  

This isn’t just about saving costs. It’s about operating at the same speed and efficiency as US competitors, without setting up a US entity or managing complex cross-border banking. Aspire gives you the infrastructure to compete globally while staying focused on growing your business.

Learn more about Aspire's payment solutions and how we help businesses scale across borders.

Frequently asked questions

What is the difference between an ACH routing number and an account number?

An ACH routing number identifies the bank that processes the payment. It tells the ACH network where the money should go. An account number identifies your specific bank account. It ensures the money is credited to you, not someone else at the same bank. Both are required for ACH transfers. The routing number gets the payment to the right bank, and the account number gets it to the right account.

Is ACH the same as ABA or wire routing?

Not always. An ACH routing number is a type of ABA routing number, but banks may use different routing numbers for different payment types. Some banks use the same number for cheques, ACH, and wires. Larger banks often use separate numbers. Using a wire routing number for ACH will cause the payment to fail.

Can a Singapore company receive ACH payments?

Yes, but not through a Singapore bank account. ACH is a US domestic payment system. It only works between US financial institutions. To receive ACH payments, a Singapore company needs a US-based USD account with a routing number and account number. Many fintech providers offer this setup as well.

What happens if you use the wrong routing number?

Using the wrong routing number leads to failed or delayed payments. If the routing number is invalid, the payment is rejected within 1–2 business days. If the routing number is retired or incorrect, the payment may bounce back after 4–9 business days. If a wire routing number is used for ACH, the payment is rejected immediately. In most cases, processing fees still apply, and business relationships can be affected.

Are ACH transfers cheaper than wire transfers?

Yes. ACH is significantly cheaper than wire transfers. ACH payments usually cost USD 0.20–1.00 per transaction. Domestic wires typically cost USD 25–40, and international wires cost even more.

For regular US payments, ACH offers substantial cost savings. Wires are best reserved for urgent or high-value transfers.

Is ACH routing the same as SWIFT?

No. They serve completely different purposes. ACH routing numbers are used for US domestic payments in USD. SWIFT codes are used for international bank transfers across multiple countries and currencies.

Is ACH the same as a routing number?

No. ACH is the payment network. A routing number is the bank identifier used within that network.

What is an example of an ACH routing number?

Bank of America’s ACH routing number for New York accounts is 021000322. Other banks use different numbers based on state and transaction type.

Can ACH be used for international transfers?

ACH is designed for domestic US payments only. It cannot send money directly from a Singapore bank account to a US bank account. Some businesses use ACH by holding a US-based USD account through a fintech provider. This allows domestic ACH payments within the US system.