Is there a way to set the default value for Net of Retainage flag to Yes on all invoices?

Most businesses invoice with retainage amount deducted on the invoice total. Hence it would be easier if the Net of Retainage flag is Y by default on all invoices. I could not find a way to set this value to Y for all invoices including IDR invoices. Any guidance will be greatly appreciated.

I tried page customization but although it seems to work, it gives and error every time you save a new invoice.