Cost of sales calculation for top task billing projects

Hello,

do any one have information about how the billing extension to calculate cost of sales for project using top taks billing should work? I have the issue that having top task for billing will calculate the cost of sales wrongly.

Actually the issue is when the actual cost do not equal the budgeted cost then the variation of the cost goes to the first task recognizing revenue and do not get spread through the task.

Thanks