A folder structure and file names your accountant will thank you for

Make one folder per year, one folder per month inside it, and a few side folders for what is not monthly. Then give every file a name that starts with the document’s date, followed by the seller and the invoice number. Your accountant can find any document from a bank line in seconds, and so can you in five years’ time.

Year and month folders, plus side folders

The VAT Act asks you to keep the invoices you issue and receive divided by settlement period, the month or quarter you report VAT for. They must be easy to find, authentic, intact and legible until the tax can no longer be collected. For most businesses the period is a month (a few small VAT payers settle quarterly), so the month is your main folder:

Business/
  2026/
    01-January/
    02-February/
    ...
    09-September/
    -Contracts/
    -Letters/
    -Car/
  2027/

A few rules make this work:

• Put the number first in each month folder: 09-September, not September. The folders then sort in calendar order, and the name works in any language (09-Wrzesień is just as good).
• Call the year folder by the year alone: 2026, and keep only that year’s documents in it. When its keeping period ends, you can see at once what may go.
• File by the date printed on the document, not the day it reached you. An invoice dated 30 September that arrives on 3 October goes into September, because that is where your accountant looks. Tell them it came late, though: VAT on a cost invoice can be deducted no earlier than the month you received it.
• Side folders hold what does not belong to one month: contracts, letters from ZUS (the social insurance institution) or the tax office, the car’s papers, your registration documents. Start their names with a dash (-Contracts) so they stand apart from the months.

Should a month have Sales, Costs and Statements inside it? With a few dozen documents a month, a single folder sorted by date is easier to scan. With more, split it. Either way, keep the bank statements easy to spot: they are the record that everything else is checked against.

Tip: a sp. z o.o. (limited company) can add a -Company side folder for resolutions, papers from the KRS (the National Court Register) and the annual financial statements. They are not monthly documents, but you need them every year.

A naming pattern that works

A good name answers three questions without opening the file: when, from whom, and which document. Build it in this order:

Examples of complete names:

Four small habits save a lot of trouble:

1. Replace slashes and colons with dashes. Polish invoice numbers are often written FV/123/09/2026, and a file name cannot safely hold a slash on a Mac or on Windows. FV-123-09-2026 reads the same.
2. Keep the original currency. Write 24.60 EUR, not a złoty amount you worked out yourself. In a KPiR (the tax book most sole traders keep), the conversion to złoty is noted on the document or in an attachment, and your accountant or your software does it at the official rate.
3. Use a short seller name you would search for: Adobe, not Adobe Systems Software Ireland Ltd, unless you want the full name.
4. Leave the number out only when there is none, as on a till receipt. The date and the amount then do the job.

Why not keep the name the supplier gave?

Because it describes the supplier’s system, not your month. Downloads arrive as invoice.pdf, Invoice-A0B1C2.pdf, faktura (3).pdf or a long string of digits. A folder of those tells you nothing, and three problems follow:

• Files overwrite each other. The same portal often gives every month’s invoice the same name. Save September’s invoice.pdf over August’s and August is gone.
• Duplicates slip in. invoice (1).pdf may be a second invoice or the same one downloaded twice. Your accountant has to open both to know, and offices charge for that kind of work: ifirma’s price list (checked 24 September 2026) charges 2 PLN for each duplicated cost document.
• Nothing sorts. Without the date at the front, the folder is in the order someone else chose.

The name is only a label. What counts for tax is the document itself, so rename freely: changing the file name changes nothing inside the invoice.

Google Drive, iCloud or Dropbox?

Any of them. The law cares about access, not about the brand. A business based in Poland keeps its invoices in Poland, unless they are stored electronically in a way that gives the tax office online access to them. On request, you must give the tax office access without delay, and for electronic invoices, let it download them and process their data. A cloud drive can meet that, but the law does not name any service, so if you are unsure about your set-up, ask your accountant.

Choose the drive by what you will do with it:

Keep the folder for years, not months. Tax documents are kept 5 years from the end of the year in which the tax was due. For a sole trader:

A company keeping full accounts must keep its books and documents for at least 5 years from the start of the year after the financial year. For tax, it keeps them until the tax for that year can no longer be collected, which is usually a year later. Invoices issued in KSeF (the national e-invoicing system) are stored there for 10 years from the end of the year they were issued. Receipts, foreign invoices and statements are not, so your folders are the only complete copy. Our guide on how long to keep documents covers the exceptions.

For foreigners: keep invoices in the language they came in. The tax office can ask for a Polish translation, at your cost, during proceedings or an audit. An English file name is perfectly fine.

How Komplet files documents for you

Komplet, our free Mac app, does the renaming and filing described above, into folders you choose on your own Mac or cloud drive. Nothing is uploaded to us.

• Drop a file on the app’s menu-bar icon or its window. It reads the PDF’s text, or uses on-device OCR (text recognition) for scans and photos, in Polish and English, and finds the seller, NIP, invoice number, date, amount and currency.
• It names the file date seller number, with the seller’s name as the document prints it, for example 2026-09-02 Adobe Systems Software Ireland Ltd IEE2026000110973.pdf, with slashes and colons turned into dashes. It takes the name from the document’s text, never from the old file name (it keeps the old name only when it could read nothing). If you correct the seller, number or date, the file is renamed to match, and if you change its month, it moves to that month’s folder.
• It files into your year and month folders. It keeps the month folders you already have, whatever you called them (09-SEPT, 05-MAI), and creates 09-SEPTEMBER when a month has none yet. It never overwrites a file: a second document with the same name becomes … 2.pdf. It warns you when you add the same file twice.
• Side folders that start with a dash are indexed as other documents, not as part of a month.
• Bank statements are filed into their month under the account’s name and last four digits, for example 2026-09-30 ING PLN account ·1234.pdf, and each payment is paired with the document that explains it, where the app finds one.
• “Prepare for my accountant” builds one folder for the month: every document under a readable name, the statements in their own folder, a Summary.csv and a Summary.pdf, plus a ZIP you can email. The month package guide shows what is inside.

It does not keep your books or send anything to the tax office. It keeps the folders tidy so whoever does can work quickly.

What to do next

1. Create 2026 with twelve numbered month folders and the side folders you need.
2. Pick one cloud drive, and set up a second copy somewhere else.
3. Rename this month’s files to date seller number, and file each by the date printed on it.
4. Ask your accountant how they want the month handed over, and by which day.
5. Make it a weekly habit, as in organising invoices and receipts, so the month is ready on the 1st.