A state withholding certificate (W-4) is used by employers to determine the amount of an employee's paycheck to withhold for state income tax.

Fill any PDF form with Anvil’s API

Anvil’s PDF Fill API and intuitive UI make it easy for teams to templatize any PDF and fill it over API. Quickly build document templates and levarge pre-programmed field types with built-in validation as well as field aliases that allow standardization of field keys across PDFs. Once set up, Anvil provides a unique endpoint and an example payload for testing.

Common employment forms are ready to go

We’ve created document templates and Workflows for the most commonly used hiring and payroll forms. Use our pre-set field aliases or customize to use your own that match your application schema. Need a form that hasn’t been templatized? Upload it to Anvil to quickly templatize and start filling it out over API.

You’re just one quick integration away from completely accurate, automated employment documents.

Try it! Fill out the Illinois W-4 over API with your own data

Need to complete these forms for your clients? Copy this template and start filling out the Illinois W-4 with a single API request.