Best Finance & Payments APIs in 2025

In the ever-evolving landscape of finance and payments, APIs play a crucial role in facilitating various functionalities that enhance user experience and streamline processes. This blog post delves into the top 10 APIs in the finance and payments category, providing developers with a comprehensive overview of their features, capabilities, and practical applications. Each API will be discussed in detail, including its endpoints, response structures, and potential use cases, ensuring that developers can effectively integrate these tools into their applications.

1. Loan Amortization Calculator API

The Loan Amortization Calculator API is designed to calculate the repayment installments for any loan provided to it. Amortization refers to the process of paying off a debt over time through equal installments, where each payment consists of both principal and interest. This API is particularly useful for developers looking to create web-based loan calculators or for financial institutions that want to provide users with detailed installment information before they apply for a loan.

Endpoints

Calculate Repayment

This endpoint returns a detailed loan repayment schedule. Developers can pass loan details such as loan amount, interest rate, loan term, and payment frequency to receive a comprehensive breakdown of each installment.

{
  "date": "2020-01-02",
  "interest": 5.833333333333334,
  "principal": 8330.660060136574,
  "payment": 8336.493393469907,
  "balance": 91669.33993986342
}

In the response, the key fields include:

• date: The date of the payment.
• interest: The interest portion of the payment.
• principal: The principal portion of the payment.
• payment: The total payment amount.
• balance: The remaining loan balance after the payment.

Developers can use this data to display amortization schedules in their applications, allowing users to track their loan payments over time.

Common Use Cases

• Creating a web loan amortization calculator for users to visualize their payment schedules.
• Providing installment information for users applying for loans through financial institutions.

2. Interests Calculator API

The Interests Calculator API allows developers to incorporate compound interest calculations into their applications effortlessly. By entering the principal amount, interest rate, and time period, users can obtain the calculated compound interest amount. This API is invaluable for financial planning applications, investment analysis, and loan calculators.

Endpoints

Get Interests

This endpoint requires users to input the initial investment, annual contribution, duration, and interest rate to calculate the compound interest.

{
  "apy": "5.61%",
  "compound_interest": "€258.49",
  "investment_returns": "€4862.55",
  "principal": "$5000",
  "rate": "5.50%",
  "time_months": "12 M"
}

Key fields in the response include:

• apy: Annual percentage yield.
• compound_interest: The total compound interest earned.
• investment_returns: Total returns on the investment.
• principal: The initial investment amount.
• rate: The interest rate applied.
• time_months: Duration of the investment in months.

This data can be used to help users understand the growth of their investments over time.

Common Use Cases

• Financial planning applications to calculate future savings and investment growth.
• Investment analysis tools to evaluate different investment opportunities.

3. Textify Money API

The Textify Money API simplifies the conversion of numeric representations into text values, making it easier for developers and researchers to extract valuable information from financial data. This API is particularly useful for applications that require the conversion of monetary values into a human-readable format.

Endpoints

Get Textify

This endpoint allows users to convert a numeric value into its text representation by specifying the number and the desired language.

{
  "success": true,
  "message": "The getTextFromNumber was successfully completed!",
  "data": "einhundert"
}

Key fields in the response include:

• success: Indicates whether the conversion was successful.
• message: A message detailing the result of the operation.
• data: The text representation of the input number.

Developers can use this API to enhance the readability of financial documents and reports.

Common Use Cases

• Billing systems to convert numerical values into written monetary representations on invoices.
• Personal finance management applications to display monetary values in text format.

4. Currency Conversion Engine API

The Currency Conversion Engine API provides real-time exchange rates and accurate currency conversions, making it an essential tool for applications that deal with international transactions. This API allows developers to integrate currency conversion features seamlessly into their applications.

Endpoints

All Currencies

This endpoint retrieves a list of all available currencies.

["USD", "EUR", "GBP", "JPY", "AUD", "CAD"]

Developers can use this data to populate currency selection fields in their applications.

Currency Conversion

This endpoint requires users to specify two currencies and an amount to convert.

{
  "from": "USD",
  "to": "EUR",
  "amount": 100
}

Key fields in the response include:

• from: The source currency code.
• to: The target currency code.
• amount: The amount to convert.

This data can be used to display converted amounts in user interfaces, enhancing the user experience during transactions.

Common Use Cases

• E-commerce platforms to provide real-time currency conversion for international customers.
• Travel booking applications to help users convert prices into their local currency.

5. Forex API

The Forex API provides access to real-time exchange rates for over 190 currencies, enabling applications to perform accurate currency conversions and facilitate international transactions. This API is essential for businesses and developers involved in foreign exchange operations.

Endpoints

Currencies Available

This endpoint retrieves a list of all supported currencies.

{
  "AED": "United Arab Emirates Dirham",
  "AFN": "Afghan Afghani",
  "ALL": "Albanian Lek"
}

Developers can use this data to create currency selection interfaces in their applications.

Get Latest Rates

This endpoint provides the latest exchange rates based on USD.

{
  "USD": 1,
  "EUR": 0.9147,
  "JPY": 145.34
}

Key fields in the response include:

• USD: The base currency.
• EUR: The exchange rate for Euro.
• JPY: The exchange rate for Japanese Yen.

This data can be used to display current exchange rates in financial applications.

Common Use Cases

• Financial applications to calculate expenses in different currencies.
• Travel websites to show costs in users' preferred currencies.

6. Exchange Rate Data API

The Exchange Rate Data API offers real-time rates, historical data, and effortless currency conversion for global financial transactions. This API is designed to empower businesses, travelers, and developers with accurate exchange rate information.

Endpoints

All Currencies

This endpoint retrieves a list of all available currencies.

{
  "success": true,
  "data": {
    "USD": "United States Dollar",
    "EUR": "Euro",
    "GBP": "British Pound"
  }
}

Developers can use this data to create user-friendly currency selection options in their applications.

Conversion

This endpoint allows users to convert between two specified currencies.

{
  "success": true,
  "message": "OK",
  "date": "2023-09-06",
  "currency": {
    "from": "USD",
    "to": "EUR"
  },
  "result": {
    "raw": 0.9147,
    "formatted": "€0.91"
  }
}

Key fields in the response include:

• success: Indicates whether the conversion was successful.
• message: A message detailing the result of the operation.
• currency: The currencies involved in the conversion.
• result: The converted amount.

This data can be used to display conversion results in financial applications.

Common Use Cases

• E-commerce platforms to enable customers to view prices in their local currency.
• Travel applications to assist users in managing expenses abroad.

7. Currency Calculator API

The Currency Calculator API facilitates global financial transactions by providing accurate currency exchange rates and seamless integration for diverse applications. This API is essential for businesses and developers looking to implement currency conversion functionalities.

Endpoints

Get Currencies

This endpoint retrieves a list of all available currencies.

{
  "status": "success",
  "currencies": [
    {
      "code": "USD",
      "name": "United States Dollar"
    },
    {
      "code": "EUR",
      "name": "Euro"
    }
  ]
}

Developers can use this data to create currency selection interfaces in their applications.

Conversion

This endpoint allows users to convert between a base currency and one or more target currencies.

{
  "status": "success",
  "source": "USD",
  "amount": 1,
  "results": [
    {
      "currency": "EUR",
      "price": 0.9308
    },
    {
      "currency": "JPY",
      "price": 147.268
    }
  ]
}

Key fields in the response include:

• status: Indicates the success of the operation.
• source: The base currency used for conversion.
• amount: The amount being converted.
• results: An array of conversion results for each target currency.

This data can be used to display conversion results in user interfaces, enhancing the user experience during transactions.

Common Use Cases

• E-commerce websites to display product prices in multiple currencies.
• Travel booking platforms to help users compare prices in their preferred currency.

8. Mortgage Calculator API

The Mortgage Calculator API simplifies the complexities of home financing by providing detailed mortgage insights. This API is designed to help users understand their financial commitments related to mortgages, making it an invaluable tool for homebuyers and financial advisors.

Endpoints

Calculate

This endpoint receives loan details and returns calculated mortgage payments.

{
  "monthly_payment": {
    "total": 1001,
    "mortgage": 1001,
    "property_tax": 0,
    "hoa": 0.0,
    "annual_home_ins": 0
  },
  "annual_payment": {
    "total": 12015,
    "mortgage": 12015,
    "property_tax": 0.0,
    "hoa": 0.0,
    "home_insurance": 0.0
  },
  "total_interest_paid": 100374
}

Key fields in the response include:

• monthly_payment: Breakdown of monthly payments, including total, mortgage, property tax, and HOA fees.
• annual_payment: Breakdown of annual payments.
• total_interest_paid: Total interest paid over the life of the mortgage.

This data can be used to help users assess their financial commitments and make informed decisions regarding home purchases or refinancing options.

Common Use Cases

• Integrating the API into real estate websites to help prospective homebuyers visualize monthly mortgage payments.
• Financial planning tools to assist clients in long-term mortgage planning.

9. Payment Card Verification API

The Payment Card Verification API is designed to validate credit card information during online transactions. This API ensures the accuracy and legitimacy of credit card data, providing a critical layer of security for digital payments.

Endpoints

Card Validation

This endpoint validates credit card data based on its Bank Identification Number (BIN).

{
  "status": 200,
  "success": true,
  "isValid": true,
  "message": "The BIN number is valid.",
  "data": {
    "bin_iin": "453936",
    "card_brand": "VISA",
    "card_type": "CREDIT",
    "issuer_name_bank": "CITIBANK KOREA INC.",
    "iso_country_name": "KOREA, REPUBLIC OF"
  }
}

Key fields in the response include:

• isValid: Indicates whether the card is valid.
• card_brand: The brand of the card (e.g., VISA, MasterCard).
• card_type: The type of card (e.g., CREDIT, DEBIT).
• issuer_name_bank: The name of the issuing bank.
• iso_country_name: The country of issuance.

This data can be used to enhance fraud prevention measures and ensure secure transactions.

Common Use Cases

• Verifying payment card data during e-commerce transactions.
• Validating payment cards for subscription services to maintain uninterrupted billing.

10. Document Parser API

The Document Parser API automates workflows by extracting information from lending documents with high accuracy. This API leverages Generative AI and Optical Character Recognition (OCR) to provide near 100% accurate results, making it an essential tool for financial institutions.

Endpoints

Generate Session ID

This endpoint generates a session ID for document parsing.

{
  "id": "",
  "url": "https://demo-auth-sog3xlfxxq-et.a.run.app?access_token=HlxLeaU63kFotWFklz00XG2QTALG&id=<>&client_id=<>&user_id="
}

Developers can use the session ID to authenticate requests for document parsing.

Invoice Parser

This endpoint extracts information from invoices. Users must call the authorization endpoint and pass the session ID obtained from the Generate Session ID endpoint.

{
  "invoice_number": "INV-12345",
  "date": "2023-09-06",
  "total_amount": "€1500",
  "vendor_name": "ABC Supplies"
}

Key fields in the response include:

• invoice_number: The number of the invoice.
• date: The date of the invoice.
• total_amount: The total amount due on the invoice.
• vendor_name: The name of the vendor.

This data can be used to automate invoice processing and improve operational efficiency.

Common Use Cases

• Automating invoice processing workflows in financial institutions.
• Extracting data from lending documents for analysis and reporting.

Conclusion

In conclusion, the APIs discussed in this blog post represent a diverse range of functionalities within the finance and payments category. From loan amortization calculations to currency conversions and document parsing, these APIs provide developers with powerful tools to enhance their applications. By understanding the features, endpoints, and potential use cases of each API, developers can effectively integrate these solutions into their projects, ultimately improving user experience and operational efficiency. As the financial landscape continues to evolve, leveraging these APIs will be essential for staying competitive and meeting the needs of users in an increasingly digital world.