Sage Accounting Canada

Is it possible to change the description in a sales entry once it has been posted and had a payment applied to it?

I have a large number of cheques in my cheques on hand list that are old and have already been deposited. Does anyone know how to delete these?

How can I mark a $0 Sales Invoice as paid? I had to create this invoice to make a line-item adjustment (items were same price) so my invoice comes to $0.00 and is now marked as outstanding and I want to clear it from 'awaiting payment'.