You should also know that withholding certificates only show the taxes paid by the client and not what you have invoiced. If, for example, you have a pending payment, this will not appear on the document.
The tax withholding russian numbers certificate is a fundamental pillar in the Spanish tax system, playing a crucial role for taxpayers, financial institutions and the Tax Administration.
Income Tax Return: This is essential for the correct filing of the income tax return. Taxpayers must use the information provided in this document to comply with their annual tax obligations.

Verification and control: Allows taxpayers to verify whether the withholdings applied by the payer match what was declared, providing an opportunity to correct possible errors.
Regulatory compliance: Helps the Tax Administration to control and ensure compliance with tax obligations by taxpayers and payers.