James, get the bank statements and the client has to explain what deposits were not income, if any. If they cant is it possible they missed expenses? You start by literally reconstructing the income and expenses. Unless of course the client admits they were under-reporting. I assume the client is denying it.
The goal is to either prove the client can explain any unreported income as (1) not income or (2) not taxable because of additional expenses. If they cant, and you have unreported income, then step 2 is can you come up with additional expenses or other items to reduce and limit the damage.
Get a good retainer up front…
