By Natalie - September 2, 2025
Categories: Bookkeeping, Taxes

If you own an automotive repair business, there’s a date you don’t want to ignore: September 15. That’s the deadline for making your third-quarter estimated tax payment for 2025.

While it might feel like just another item on your already full to-do list, estimated taxes are a critical part of keeping your business in good financial standing. Missing the deadline can lead to IRS penalties, interest charges, and unnecessary stress, all of which can take your attention away from your customers and your shop floor.

This guide will walk you through what estimated taxes are, who needs to pay them, how to calculate your payment, and how to make the process easier going forward.

Who Needs to Make Estimated Tax Payments?

Estimated taxes are not just for big corporations. If you operate your auto repair shop as a sole proprietor, partnership, LLC, or as an S-corp shareholder, you may need to pay estimated taxes if you expect to owe at least $1,000 in federal taxes for the year after subtracting any withholding or credits.

This typically applies if:

  • You don’t have taxes withheld from your income (common for self-employed shop owners).
  • You have other income from parts sales, fleet contracts, inspections, or towing.
  • Your earnings fluctuate, but you consistently make a profit.

Many shop owners are surprised to learn they fall into this category, especially if business has been good and revenue is up compared to last year.

 

How to Calculate Your September 15 Payment

The IRS provides Form 1040-ES, which includes worksheets to help you calculate your estimated taxes based on expected income, deductions, and credits for the year.

For automotive repair businesses, this means looking beyond just service revenue. 

You’ll need to factor in:

  • Income from parts sales

  • Any other shop-related income, such as vehicle inspections or fleet maintenance contracts

If your shop’s revenue is seasonal, for example, busier during summer travel months and slower in winter, you might benefit from using the annualized income method. This approach lets you adjust payments based on actual income during each quarter, which can prevent overpaying early in the year.

If you’re unsure which method makes the most sense, our team at Three Rivers Bookkeeping can guide you through the numbers and help you calculate the right payment for your shop.

How to Pay Your Estimated Taxes

You have a few options for making your payment:

  • Online: The IRS Direct Pay system allows you to pay directly from your bank account with immediate confirmation.

  • EFTPS: The Electronic Federal Tax Payment System offers secure scheduling and tracking of payments.

  • By Mail: Using a payment voucher from Form 1040-ES (though online is faster and more reliable).

Avoiding the Last-Minute Scramble

Many auto repair shop owners find themselves scrambling in September because they didn’t plan ahead. The good news? A little bookkeeping discipline can make these deadlines far less stressful.

One of the easiest strategies is to set aside a percentage of your income each week in a separate savings account labeled “Taxes.” Even 20–25% of your net income can build up quickly and ensure you’re ready for each quarterly deadline.

Consistent bookkeeping also makes a huge difference. When you keep your books up to date — tracking revenue, expenses, and profit in real time — your estimated tax calculations are more accurate, and you’re less likely to face unpleasant surprises at year-end.

One of our favorite tools for auto repair shop owners is QuickBooks Online. It’s easy to use, integrates with most shop management systems, and lets you see your financial picture at a glance without guessing or waiting until tax time.

👉 Sign up for QuickBooks Online here and start keeping your books in order year-round.

Finally, working with a bookkeeper who understands the ins and outs of auto repair businesses can take this task off your plate entirely. At Three Rivers Bookkeeping, we’ll track your income, forecast your tax obligations, and keep you ahead of every deadline so nothing slips through the cracks.

The Bottom Line

The September 15 estimated tax deadline is approaching fast. By taking care of your payment now, you’ll avoid penalties, keep your finances on track, and free up your energy to focus on what matters most…keeping your customers’ vehicles safe and running smoothly.

If you’d rather spend your time under the hood than calculating tax payments, Three Rivers Bookkeeping can help. We specialize in bookkeeping for auto repair shop owners, providing accurate financial records, tax-ready reports, and strategies that help you plan for each quarter without the stress.

Contact us today so you can meet the September 15 deadline with confidence and have a plan in place for every tax deadline that follows.