From the SAP Business One Main Menu, you have chosen:

 Business Partners Business Partner Master Data

In the Business Partner Master Data window, on the Accounting tab, on the Tax subtab , you have selected the Subject to Withholding Tax checkbox.

You have chosen the Add or Update button.

However, you have not specified a P.A.N. number, and this is required for business partners who are subject to withholding tax.

On the Tax subtab of the Accounting tab in the Business Partner Master Data window, choose the (Tax Information) button.

In the Tax Information window, in the P.A.N No. field, enter a number.

Choose the Add or Update button.