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How to structure invoice CSV & Excel files

To help you avoid upload errors - and to make sure Adfin reads all the information in your file correctly - please follow the guidance below when preparing your .csv or .xlsx invoice files.

Chris Carty avatar
Written by Chris Carty
Updated this week

💡 You can drag and drop invoices anywhere into Adfin: no need to click the 'Invoice from upload' button.


With Adfin, you can upload a wide range of invoice files - PDFs, images, and CSV or Excel files. Adfin’s intelligent capture will extract the information for you to review before sending. You can upload up to 200 invoices in a single batch, using one file type at a time.
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This guide focuses specifically on CSV and Excel uploads. You can download an example CSV template and use it as a model. Use this template as a reference to ensure your columns and formatting match what Adfin expects. Following the structure closely will help prevent upload errors.

1. General notes on file structure

Adfin expects one item per line in your CSV or Excel file.
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We combine individual line items into invoices using the Invoice Number column.
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The column name does not need to match “Invoice No” exactly — as long as the meaning is clear, Adfin will recognise and group items accordingly.

If there is no Invoice Number column:

If your file does not include any field that identifies invoice numbers, Adfin will automatically group items per customer, using the customer identification fields mentioned below (External ID → Email → Customer Name).
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Adfin will alos automatically generate an invoice number for you. We do this by using the default invoice prefix and the next number in your configured sequence, as set in your invoice settings:
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👉 https://console.adfin.com/settings/invoice-settings
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While this ensures invoices can still be created, we strongly recommend including an Invoice Number column for the most accurate grouping and tracking.

2. File size & invoice limits

Adfin can process a maximum of 200 invoices per upload.
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If your dataset contains more than 200 invoices, simply split them into separate files and upload them one at a time.

3. Date formatting requirements

To ensure accurate processing, all dates must follow UK format:

  • Invoice Issue Date: DD/MM/YY or DD/MM/YYYY

  • Invoice Due Date: DD/MM/YY or DD/MM/YYYY

Both 2-digit and 4-digit years are accepted. Incorrectly formatted dates may prevent your file from uploading successfully.

4. How Adfin handles tax rates

Adfin calculates tax using only the Net Amount and the Tax Rate. Here’s how the system decides which tax rate to use:

  • If your file includes a tax rate:

    Include a column such as “VAT rate” to specify the tax rate for each invoice.
    Adfin will use the value you provide.

5. Invoice customer matching

When you upload an invoice, Adfin will first check whether the customer already exists in your account:

  • If the customer does not exist: Adfin will automatically create a new customer record based on the details in your file.

  • If the customer already exists: Adfin will attempt to match the invoice to that customer using the following hierarchy:

  1. External ID

  2. Email

  3. Customer Name

Adfin always tries to match using the External ID first, if one is present.
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Required customer identifiers

Your uploaded invoice must include at least one of the following fields to identify the customer:

  • External ID

  • Email

  • Customer Name

For best results, we recommend including both Email and Customer Name as a minimum.
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Using External IDs from other platforms

If you export invoices from another system, those files often contain External IDs specific to that platform. Adding these IDs to your customer records in Adfin ensures the most accurate and reliable matching.
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How to add External IDs to customers in Adfin

  1. Go to the Credit control view

  2. Select the customer you want to update

  3. Hit 'Update' the on the Customer information section

  4. Enter the correct External ID

  5. Save your changes

Adding External IDs helps Adfin recognise and match your customers consistently across systems, reducing duplicates and improving data accuracy.

6. Credit note support

At this time, credit notes cannot be uploaded via CSV or Excel files.

⚠️ Warning: Excel files containing formulas cannot be processed
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Adfin supports Excel files, but they must contain raw values only. If an Excel contains formulas we will not be able to load or parse it correctly.
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What to do instead:

  • Export the Excel as a CSV file and upload that instead, which avoids formula-related issues entirely.

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