Common mistakes in accounting documents

Up­dated: Septem­ber 2026

Many cor­rec­tions are caused not by com­plic­ated reg­u­la­tions but by miss­ing de­tails, late doc­u­ments or an un­clear de­scrip­tion of the trans­ac­tion.

A quick check of your doc­u­ments before you send them can save time for both you and your accountant.

Six mistakes you can avoid

1. In­cor­rect buyer or seller de­tails. Check the name, ad­dress and tax iden­ti­fic­a­tion number (NIP).
2. Miss­ing or wrong date. The date a doc­u­ment is issued is not always the date the ser­vice was per­formed or the goods were de­livered.
3. Il­legible scan. A cropped in­voice or un­read­able amounts make it im­possible to post the doc­u­ment cor­rectly.
4. Send­ing the same doc­u­ment sev­eral times. An in­voice sent by email, through the client portal and on paper may be treated as a du­plic­ate.
5. No de­scrip­tion of the busi­ness pur­pose. An un­usual ex­pense should come with a short ex­plan­a­tion.
6. Doc­u­ment de­livered after the period has been closed. It may re­quire a cor­rec­tion to the re­cords or to a tax return.

How should you describe expenses?

The de­scrip­tion should state what was pur­chased, for what pur­pose, and which part of the busi­ness, pro­ject or source of income it relates to.

Invoice and proof of payment

A trans­fer con­firm­a­tion or bank state­ment usu­ally does not re­place an in­voice. On the other hand, an in­voice alone does not always prove that pay­ment was made. Where ne­ces­sary, keep both doc­u­ments.

A consistent document flow

Agree on a single chan­nel for send­ing doc­u­ments, clear file names and a fixed monthly dead­line. If your com­pany uses sev­eral sys­tems, decide which one is the main source of doc­u­ment­a­tion.

How a doc­u­ment is re­cor­ded de­pends on the type of trans­ac­tion and the tax­payer's in­di­vidual situ­ation.