Payments and Penalties

Yes. If two-thirds of your gross income is generated from farming, a estimated general rule exception exists. If you file your return and pay the entire tax due on or before March 1st, then you are not required to pre-pay amounts with estimates.

Taxpayers with AGI under $150,000 (75,000 MFS) will have to pay 100% of their prior tax bill by the end of the year, Taxpayers with AGI over $150,000 (75,000 MFS) will have to pay 110% of their prior tax bill by the end of the year or 90% of the current year tax to avoid an underestimated tax penalty.

No. The filing of joint or separate estimated payments does not require that you are committed to filing that way.
However, you will need to advise the IRS as to how to allocate the estimate payment.
Often this can be an area of difficulty when individuals are going through a divorce and have decided to file separately after making joint estimated tax payments.

You are entitled to an automatic extension until October 15 by filing form 4868. An extension to file is not a extension of time to pay.
By filing an extension, you avoid the late filing penalty, but will have penalties on any money you owe after April 15. (April 17, 2012)

Basically, you will have to file an amended return (IRS Form 1040X)to include or exclude items of income or expenses that you didn’t include on the return already filed. If you know you are waiting for some information, do not file your return on 4/15/XX.) You are entitled to a six month extension to file(not to pay). Try to avoid filing amended returns. They are subject to additional scrutiny by the IRS.