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Calculators
Do I need to make a payment with my extension?
To avoid an IRS underpayment penalty, use the Safe Harbor method to calculate whether you need to send an additional payment with your extension of time to file by April 15th.
To meet Safe Harbor requirements, pay:
- At least 100% of the previous year’s total tax owed, or
- 110% if your AGI was >$150k for the previous year
Note: Safe Harbor payment does not protect you from other IRS penalties or interest, such as late filing, late payment or accuracy-related penalties.
Use the Safe Harbor Tax Calculator to find out if you need to make a payment. For more details and information on state filing obligations, watch the video below.

2024 Safe Harbor Tax Calculator
Calculating your quarterly estimated tax payment
As a business owner, you must make estimated tax payments throughout the year to avoid underpayment penalties and other tax surprises. These payments cover both income and self-employment tax.
Using this Basic Quarterly Estimated Tax Calculator, you can calculate a general estimate of how much you should pay each quarter to stay in compliance.
Calculator presumes 22% income tax + 15.3% self-employment tax.
Note that determining the most efficient quarterly estimated tax amount requires a more detailed approach that analyzes your full financial situation. This service is available to Accountability Services clients, depending on your engagement.

Basic Quarterly Estimated Tax Calculator
Estimating monthly payments on a new loan
Use this basic Loan Calculator to compare loan terms and estimate your monthly payment.
This tool makes the following assumptions:
- Fixed interest rate for the life of the loan
- Standard amortization formula for equal monthly payments
- Monthly (not daily) compounding
- Payments made at the end of each period
- Does not factor in loan origination fees, taxes or insurance

Loan Calculator
Generate amortization schedule
The Loan Amortization Calculator uses the same assumptions as the Loan Calculator to build out a full amortization schedule for the life of the loan.
