Once you have 1-2 of the contract, any accountant-freelancer will bring you this "balance" on the simplified taxation for a candy bar or 500 rubles. There is nothing complicated, just like in school. "income" and "expenses". Since going on the simplified taxation, spending all do not care, so that you can write only the income and visitat 6% of them.
Statements can be taken by mail with return receipt requested. well, or I Servisa, kotoryh you wrote. Of the pitfalls of the once a year 16 Tr non-budgetary (pension).
If the truth is 2 of the contract high, it is better to work under contract with this customer and let him pay the tax for you (with your money), but get rid of the pension bubnoplyasok. You're retiring to spit, right?