Power BI: Combine Multiple CSV Files From a Folder

Quick Answer: In Power BI Desktop, choose the Folder connector, point it at the folder of CSVs and select Combine & Transform Data. Fix headers and junk rows once in the Transform Sample file query, delete the broken final step in the output query, set data types, and keep the Source.Name column. Add each new month's CSV to the folder and select Refresh.

To combine multiple CSV files in Power BI, point the Folder connector at a folder holding all your monthly bank exports and let Power Query's Combine Files build one table. You clean a single sample file and Power BI applies the same steps to every file. A new month then needs only a refresh, provided every CSV shares the same columns.

Before you start: get the folder right

Microsoft's combine CSV files guide is blunt about the precondition: the files "all have the same structure and the same extension." For bank statements that means:

• One account per folder. A checking account export and a credit card export usually have different columns. Combine them separately and append later if you need to.
• Same export settings every month. If you once ticked an extra column in your bank's download dialog, that file will not line up.
• Only CSVs in the folder. The Folder connector includes files in subfolders too. A stray PDF or an Excel copy will break the combine unless you filter it out.
• Sensible file names, such as 2026-01 checking.csv. The name ends up in your data, so make it useful.

If some months only exist as PDF statements, convert those first so they have the same columns as the rest. QuickBankConvert turns PDF statements into CSV rows with date, description, category, signed amount and balance, so a year of PDFs comes out in one consistent layout; check that the columns match any CSVs you exported from the bank directly. The PDF to CSV page shows the output.

How do you combine the CSV files in Power BI?

1. Connect to the folder

Microsoft's Folder connector steps for Power Query Desktop:

1. Select the Folder option in the connector selection.
2. Enter the folder path or select Browse, then OK. A list of every file in the folder, and in its subfolders, appears.
3. Choose one of three buttons: Combine & Transform Data opens the combined result in the Power Query Editor; Combine & Load loads it straight into the model; Transform Data opens the raw file list for editing first.

Pick Combine & Transform Data for bank statements. You will need to clean something.

If the folder contains files you do not want, choose Transform Data instead, filter the Extension or Folder Path column to keep only your CSVs, then select the Content column and use Combine files on the Home tab. Microsoft's combine files overview recommends filtering this way.

2. Accept the Combine files dialog

Power Query analyzes the example file (the first file by default) and picks the Text/CSV connector. You can choose a different Example file from the drop-down, which is worth doing if your first file is an unusual month. There is also an optional Skip files with errors setting. Leave File origin, Delimiter and Data type detection at their defaults unless the preview looks wrong, then select Transform data in the lower-right corner.

3. Clean the Transform Sample file query

Power Query creates several queries for you: an example query named Transform Sample file, a function in the Helper queries group that applies it to every file, and the output query that stacks the results. All of them sit in a group whose name starts with Transform file from.

Make your fixes in Transform Sample file, never in the output query. Every step you add there runs against each CSV. Typical bank fixes:

• Remove top rows if the bank puts account name, date range or a disclaimer above the column headers. Select the table icon in the upper-left corner of the preview, choose Remove top rows, and enter the number of rows.
• Use first row as headers from the same table icon menu.
• Drop any totals line at the bottom of the export in this same query, so totals are not counted as transactions.

4. Repair the output query

Go back to the output query. Microsoft documents what you will probably see: an error reading "The column 'Column1' of the table wasn't found." The last step was written against the old column names. Delete that step in Applied steps using the X beside it, and the table appears correctly.

5. Set data types

The combined columns arrive without proper types. For a bank table:

Microsoft describes Fixed decimal number, also called Currency, as always precise, which suits money better than Decimal number. You can set types from the icon to the left of each column heading.

If dates turn into errors, the CSV probably uses a different date order from your computer's regional setting. Right-click the column heading, select Change type, then Using locale, and choose the data type and locale that match the file, for example English (United Kingdom) for day/month/year, as Microsoft's data types article shows.

6. Verify, then load

Open the filter on Source.Name to list every file that was combined. If you see "List might be incomplete", select Load more. Each month should appear exactly once. Then load the table into your model.

What usually goes wrong with bank CSVs?

Overlap is the one people miss. If you downloaded "last 90 days" twice, the same transactions sit in two files. Power Query will happily stack both.

How do you refresh when a new month arrives?

Drop the new CSV into the same folder, using the same export settings, and in Power BI Desktop select Refresh on the Home tab of the ribbon. The new file goes through the Transform Sample file steps automatically.

If you published the report to the Power BI service, refresh works differently. Microsoft's refresh documentation explains that the service connects to the data sources directly rather than to your desktop file, and that a gateway must be installed and running to reach on-premises sources; Folder is on the list of sources the on-premises data gateway supports. A folder on your laptop therefore needs a gateway before scheduled refresh can work in the service.

For importing a single statement CSV rather than a folder, see our guide to importing bank statements into Power BI. If you would rather merge the files before Power BI sees them, merging multiple CSV bank statements covers Excel, and the PowerShell merge guide covers a scripted approach. Converting PDF months is covered by the free account's CSV downloads for a few statements a month; see pricing for more.

Related guides

• Import bank statement data into Power BI
• Merge multiple CSV bank statements into one file
• PowerShell: merge CSV files
• Convert PDF statements to CSV