Determining how much to send the IRS can feel like a guessing game, especially if your freelance income fluctuates. There are two primary strategies to ensure you pay enough to avoid penalties:

1. The Safe Harbor Rule (The Exact Method)

The IRS won't penalize you for underpayment as long as your estimated payments meet one of these "Safe Harbor" requirements:

• You pay 90% of your estimated tax liability for the current year.

• You pay 100% of your tax liability from the previous year (or 110% if your Adjusted Gross Income last year was over $150,000).

Many established business owners use the previous year's method. They simply look at their total tax bill from last year, divide it by four, and pay that exact amount each quarter.

2. The Percentage Method (The Rule of Thumb)

If this is your first year in business or your income is highly unpredictable, the Safe Harbor rule might be tough to apply. A highly effective strategy is to transfer 25% to 30% of your net business income into a dedicated tax savings account every time you get paid. When the quarterly deadline arrives, simply send the IRS whatever has accumulated in that account.

You don't need to mail a physical check (though you can, using the payment vouchers attached to IRS Form 1040-ES). The most efficient ways to pay include:

• IRS Direct Pay: A free, fast, and secure way to pay directly from your checking or savings account.

• EFTPS (Electronic Federal Tax Payment System): Another free government system that requires a brief initial setup but is excellent for managing routine business tax payments.

This IRS page provides  a link to various means for making payments: Make a Payment