Cash Under the Hood: What the IRS Actually Thinks About Your Weekend Wrench Work

Let's be real. At some point, word gets out that you know your way around a garage, and suddenly your neighbor's asking if you can sort out his truck's wheel bearings. You say sure, he hands you $200, and you think nothing of it. But somewhere in a federal building, a very boring algorithm might beg to differ.

Tax law and torque specs don't usually share the same conversation, but if you're doing any kind of paid work out of your home garage — even casually — it's worth knowing where you stand before you get a letter you don't want.

Hobby vs. Business: The Line That Actually Matters

The IRS draws a pretty sharp distinction between a hobby and a business, and the difference has serious financial consequences. A business is something you run with the intent to make a profit. A hobby is something you do for fun, even if it occasionally generates a little cash.

Here's the kicker: hobby income is still taxable. You read that right. If your neighbor pays you $200 to do his wheel bearings, that's income. The old "it's just cash" mindset doesn't hold up if you ever get audited.

The IRS uses a rough presumption that if your activity shows a profit in at least three out of five consecutive years, it's probably a business. But they also look at a list of other factors — things like how much time you put in, whether you depend on the income, your history of losses, and whether you're actually trying to improve your operation over time.

If you're just doing the occasional favor-for-cash on weekends, you're probably operating in hobby territory. But "probably" isn't "definitely," and that gap is where people get into trouble.

What Hobby Income Used to Get You (And Doesn't Anymore)

Before the Tax Cuts and Jobs Act of 2017, hobby enthusiasts could deduct hobby-related expenses — things like tools, supplies, and shop consumables — up to the amount of hobby income they reported. It wasn't perfect, but it softened the blow.

That deduction is gone now. Suspended through at least 2025, those miscellaneous itemized deductions are off the table for most filers. So if you're reporting $1,500 in casual garage income, you can't offset it with the $800 you spent on supplies that year. You owe taxes on the full amount.

This is a meaningful change that a lot of DIYers haven't caught up with yet.

Running It Like a Real Business: Pros and Cons

If your garage work is more than just occasional — say you're regularly flipping cars, doing paid tune-ups, or running a small side operation detailing vehicles — it might actually make more sense to operate as a legitimate business. A sole proprietorship or single-member LLC gets you access to Schedule C deductions that hobby filers can't touch.

We're talking:

• Tools and equipment (including depreciation on big-ticket items)
• Shop supplies — fluids, consumables, fasteners
• A portion of your utility bills if you use your garage exclusively for the business
• Business-use miles driven for parts runs and pickups
• Liability insurance, if you carry it

The tradeoff? You'll owe self-employment tax on top of income tax — currently 15.3% on net earnings up to a certain threshold. That stings. But if your operation is generating real money, the deductions can more than compensate.

The other thing worth considering: structuring as an LLC gives you some separation between your personal assets and any liability that might arise from your work. Which brings us to the next thing nobody wants to talk about.

When Friends Pay You and Something Goes Wrong

Let's say you replace a friend's brake pads. He pays you $100. Three weeks later, he has a brake issue — maybe related, maybe not — and he's looking for someone to blame.

In most states, doing mechanical work for compensation without a proper license exposes you to real legal risk. Even among friends. Even for small amounts. If something goes sideways and there's a clear exchange of money, you could find yourself in a civil dispute with zero professional protection behind you.

This isn't meant to scare you out of helping people — it's meant to help you think clearly about the difference between genuinely helping a buddy and quietly running an unlicensed repair operation. The former is fine. The latter is where liability starts to creep in.

Some folks handle this by structuring arrangements as "you buy the parts, I'll do the labor for free" — keeping the transaction off the books and framing it as a favor. Whether that strategy holds up legally depends on your state and your specific situation, but it's a common approach in the DIY community.

Selling Cars: A Whole Different Animal

Flipping vehicles is its own tax conversation. Most states have a limit on how many vehicles a private individual can sell per year before they're required to hold a dealer's license — often somewhere between two and five, though it varies widely.

Beyond licensing, any profit you make selling a vehicle is generally subject to capital gains tax. Short-term gains (vehicles held less than a year) are taxed as ordinary income. If you're regularly buying, fixing, and selling, the IRS may treat that as business income regardless of how you classify it.

Keep records. Seriously. What you paid for the car, what you spent on parts, what you sold it for. A simple spreadsheet goes a long way if questions ever come up.

The Practical Takeaway

Nobody's saying the IRS is lurking outside your garage waiting to bust you for changing your neighbor's oil. But the more your weekend wrenching looks like a business — regular customers, consistent income, tools and supplies you're buying specifically for the work — the more it's worth treating it like one.

That means keeping simple records, understanding what income you're generating, and maybe spending an hour with a CPA who understands small business taxes. It's not glamorous, but neither is getting a tax bill you weren't expecting.

The garage is supposed to be a place where you clear your head, not a source of financial stress. A little awareness now keeps it that way.