Advance billing

Hi all,

Can you please suggest a way to deal with advance billing?

We are using billing control excel sheets to track down the advance billing, but I would like to find a way to do this automatic in Timeslips and to be able to get the overall value allocated against users when the time is coming to include the slips in the billing.

For example, we are billing annual management fees in advance and during the year some of the slips are used to cover that amount, but at the time of the billing, we need to bill in advance again for the current work. 

When running the billing report, these amounts of advance billing are showing as write ups, as we process them though Adjust time charges total. But we are processing the write offs through the same feature and in some occasions this is getting mixed with the write ups and can't track them properly.

Thanks in advance!