Hi All;

I started using Odoo about 3 weeks ago and have been absolutely thrilled with it. I'm currently starting up an IT Consulting business where I'm billing time out on contracts.

I've been able to set up contracts for my customers with price lists where required. I'm assigning time to tasks and those are turning up correctly for invoicing via the correct Analytic Accounts. All of my current customers pre-pay me for block time. While some customers negotiate a flat rate others do not. For flat rate customers I can allocate prepaid service units to keep track of hours remaining on a contract. I'm currently struggling with two issues. 

1)I can't seem to figure out how to issue a customer an invoice for their pre-payment that my Task time will deduct against. Ideally I would like to be able to send a customer an invoice up front for, say, $5000 and then have my time worked deduct from that amount until I reach the point where I need to remind them to renew. Currently my service rates are entered as products and time on tasks are invoiced selecting the appropriate product that denotes the support type utilized. I'm not certain how to invoice them in advance for products they will use later, and what would be on that advanced invoice.

2)I'm also struggling with how to bill customers at anything other than a flat rate.Since my time is offered to some clients in a tiered structure (Emergency Support, Onsite Support, Remote Support, Travel) Prepaid Service Units don't do me much good as time would be billed at varying rates. I'm thinking the best route would be for the customer's time to be applied as a pre-paid credit and deducted from as I work through that advanced amount.

Any advice that anyone might be able to offer would be appreciated. These are my last two major hurdles (for now). I'm already working for customers and racking up time, but they are still waiting for their invoices to pre-pay for time that they're already getting.