Some of my clients pay a retainer, a fixed amount per month.

We offset this against tasks managed in Zoho Projects.

For example, a client pays R350 at the beginning of the month.

We do 5 tasks for them, at a total cost of R250.

We use Zoho invoice to bill them for this, but they don't actually have to pay, since they are in credit.

They are therefore in credit for R100.

This credit rolls over to the next month.

How can we document and manage this in Zoho books?

Thanks

Brendon