The reason to pay quarterly taxes is to avoid being hit with an underpayment penalty. To avoid being penalized, the taxes you pay in during the year through withholdings and estimated taxes needs to exceed the lesser of:

1. 110% of your prior year's tax liability, or

2. 90% of your current year's liability.

Will your withholding from your job during the first part of the year exceed either of these thresholds? If not, you should probably send in some money by 9/15 along with estimated tax voucher #3 - Form 1040ES.

Please note that the government generally wants you to pay your estimated taxes evenly over the year. In your case, since you did not earn you income evenly over the year, you will want to prepare a Form 2210 as part of your tax return, and show the IRS how much income you earned each quarter.

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