Get your taxes done using TurboTax

Actually, it appears that the IRS doesn't really care based on my previous experience with this. It keeps a running tab of all your payments by designated tax year and when they were made to compute any interest.

When you file an extension you by definition do not quite know the exact amount you'll owe so you typically estimate to overpay a little bit anyway.

I recall, I got sick of filling out and filing this extra extension payment voucher (I seem to recall it had to be mailed somewhere else so more postage and nonsense to keep track of) and just kept making an additional - well-calculated - estimated payment. I have attached Form 4868 - take a look at Part II lines 4, 5, 6,7.

Basically, you estimate such that the payments match or exceed what you might owe, then the balance due becomes 0 and the amount you are paying also becomes 0 and no need to deal with extra payment vouchers.

Of course, one can do it differently and select 'Extension' in eftps.gov - but in the end all the IRS cares is that there are at least as many funds in your account as to what is owed for that tax year.

On a related note: usually, I get a refund these days due to multiple variable investments, but in previous years when I owed, I would go into TT at the time of actual filing (not extension), enter an estimated payment for the exact amount of taxes owed, get a reduction of $1-2 at that time and got a congratulation from TT for exactly balancing the owed tax to $0.

I would then go into the eftps.gov online payment system, make an estimated payment for the relevant tax year for the exact amount of taxes owed and file the return with $0 owed and $0 refund.