@ArchesNationalPark
bullet one - yes, the total will be the same. and that is because Total tax - estimated payments - withholdings = refund / still owe on April 15.
bullet 2 - not true. Very simply and generally, there is no penalty interest as long as the estimates + withholding equals 100% of last year's tax liability (or 110% for high income earners) or 90% of this years tax liability, whichever is lower, OR the amount due on April 15 is less than $1000.
So for example, last year the tax paid was $20,000 and this year's tax estimate is $30,000. There is no interest penalty as long as the estimated payments and withholdings are the lesser of $20,000 (100% of last year) or $27,000 (90% of this year), OR the amount due on April 15 less than $1000. . So as long as the withholdings and estimates are at least $27,000, there is no interest due.
But the IRS wants that calculation completed quarterly! which is the headache of Form 2210 and 2210ai!
look at the flow chart on the top of the form:
https://www.irs.gov/pub/irs-pdf/f2210.pdf
(if you decide to play with the form, you are going to check Box C in Part II)
