manual withholding tax type invoice error: document sequence

 Hello,

When i create manual WITHHOLTING TAX type invoice,it gives me error of document sequence.System doesnt provide seeded document category for withholding tax type invoice.I create a document category for withholding tax and sequence and assign to document category.But still manual withholding tax type invoice give error of document sequence.than i enable the override document category in payable option than withholding tax type invoice doesnt give error and sequence is generated.

But the question is it mandatory to enable override document category for creating manual withholding tax type invoice?