Every state has a different rate and way of calculating their taxes. Some states like PA have a flat rate of 3.07% with very few deductions or ways to change your tax liability while other states have graduated tax rates and laws more like the federal government.
Your federal rate will depend on your income bracket. Below is a link to the federal tax rates for 2019. But, she will also need to pay the 15.3% self-employment tax which is for Medicare and Social Security.
The easiest way to determine the estimated taxes is to use software like Quickbooks Self-Employed which will calculate your quarterly payments due.
As for this year, you can log into your TurboTax account and basically fill out your return and see what you will have due. There may be a penalty if payments were not paid quarterly.
Once you enter your information, there is a section called "Other Tax Situations" under the federal tax section. If you go to Other Tax forms, you can work on your estimated taxes for the following year.
Don't worry about about. Any underpayment is based on the previous year's tax liability. If she had no income and your income hasn't risen much, there will be no penalty.
Her self employment income is reduced by 7.65% (multiplied by 0.9235) before SET (self employment tax-FICA) is calculated. This, effectively makes the SET rate 14.13%, instead of the stated rate of 15.3%.
Quarterly Estimates. You should pay in quarterly estimated taxes if you don't have enough withholding taken out to cover the tax on all your income. You might be able to increase your W2 withholding, at your regular job, to account for the extra income.
You should make estimated tax payments for the current tax year if both of the following apply:
- 1. You expect to owe at least $1,000 in tax for the current tax year, after subtracting your withholding and credits.
- 2. You expect your withholding and credits to be less than the smaller of: 90% of the tax to be shown on your current year’s tax return, or 100% of the tax shown on your prior year’s tax return. (Your prior year tax return must cover all 12 months.)
TurboTax (TT) can prepare the quarterly payment vouchers. In your 2018 software, enter at:
Federal Taxes or Personal (H&B version)
-Other Tax Situations
-Other Tax Forms
-Form W-4 and Estimated Taxes - Click the Start or Update button
On the next screen answer No to the W-4 question
If your goal is just to avoid the underpayment penalty, then paying 100% of the prior year tax liability is the “safe haven”
Or you can obtain blank IRS Form 1040-ES from the IRS. The form and instructions are at this link: https://www.irs.gov/pub/irs-pdf/f1040es.pdf
You can also pay Federal directly here. Be sure to select 1040ES: