Write-off rules not permitted ( Tcode FP04 )

Hello Experts,

I am doing write-off for few documents,at FP04 screen I give required master data and press enter,it gives me error write-off rules not allowed.

So I found that there is a check box ( write off rules ),unchecked it and now I am able to proceed.

Can anybody brief me about this write-off rules ?

Best Regards

Amit