A proof invoice in CSI software is primarily a draft invoice used in legal aid cases and court proceedings, allowing a legal counsel or representative to present the fees and expenses to be charged from the client.

A legal aid claim created from a proof invoice can be sent directly to the electronic Romeo legal aid service from CSI software, provided that the necessary configurations have been completed: CSI users handling legal aid cases have been registered in the Palkeet payee register, and the corresponding information has been added to the CSI software user parameters.

However, a proof invoice can also be used during the course of a matter as a work and expense specification provided to the customer. A proof invoice is not an accountable invoice, and therefore it does not create an accounts receivable entry or transfer to accounting.

A proof invoice can be created from both open and already invoiced entries, and the transaction and expense entries on the proof invoice can be modified freely. Any changes made are only saved to the proof invoice and do not affect the original entries in the matter. Multiple versions of a proof invoice can also be created from the same entries without deleting previous proof invoices.