Karen
I had a career of 56 years in banking, including 10 as a director of the bank. But it was a U.S. bank. Commercial practices and vocabulary differ substantially among countries. Moreover, you have provided very little information: basically two lines. Nor do I know what you really want to know. I can calculate percentages til the cows come home, but numbers are created for a purpose. The purpose is unknown.
This is my best guess on the basis of the limited knowledge so far.
One document provides an ESTIMATE of 50,000 for preparing tax returns for 18 US states. I have no idea of whether (1) the contract calls for payment of time and materials at given rates, with the estimate being non-binding but merely a good-faith guess, (2) the contract specifies a fixed sum for all 18 states, namely 50,000, and the estimate was accepted as the fixed price, or (3) the contract calls for payment of time and materials at given rates subject to a ceiling of 50,000. Of course, it is possible that something else entirely was agreed upon. I have not seen the contract.
My experience is that the third option (time and materials subject to a ceiling on the total billed) is very common in the US for contracts with accounting firms. In that case, someone may want to know what is the percentage of the total expected cost being billed. If we assume that, on average, the cost of preparation per state is pretty much the same, we would predict that the cost for six more states will be about 5,000, and that about 67% of the total currently projected cost is being billed currently. That is a VERY dangerous assumption, however, The cost of preparing a tax return for California may be MUCH HIGHER than for Texas. What you can say without any risk of looking like an idiot is that approximately 67% of the states covered by the estimate are complete and have been billed.
You could also say without looking like an idiot that 20% of the estimated cost has been billed.
You really need to talk to your boss to figure out what he wants the percentage for. A number that could reasonably vary between 20 and 67 is not useful.
I am sorry to be so unhelpful, but even good bosses sometimes give unclear instructions and welcome a request for clarification.