You’re thrifty, you’re self-sufficient, you don’t waste money paying for services you can do yourself. Here at WalletPop, we understand that, and we try to accommodate you with tips and advice for doing things on your own — and cheaply.

However, there are a handful of tasks or situations when the DIY approach can backfire. You might think you’re saving money by not hiring a pro, but the results could cost you more — sometimes much more — than if you’d just paid for the professional service in the first place. Wallet Pop put together this list to check out.

8. Oil Changes

As this recent thread on Consumerist shows, there’s plenty of debate about this one. Sure, there are people who’ve been changing their own car’s oil for years with no problems, as well as plenty of us who remember our fathers underneath the family sedan in the garage, changing the oil with nary an incident.

That said, there are a few things to keep in mind if you decide to get your hands dirty: Cars are different today in many ways, and it might be hard for a backyard mechanic to reach all the right parts without specialized tools. Trying to shimmy under your car is also a losing proposition for many of us, and not knowing what you’re doing with a jack can literally kill you if you make a mistake. If you put in the wrong type of oil, too much or too little, you can seriously damage your engine, Scott Cudini, innovations manager for Jiffy Lube International, told WalletPop.

Finally, let’s talk cost. In many parts of the country, you can get a conventional oil change for around $25. Sure, buying five quarts of oil and a filter might cost you less than that, but that’s not factoring in the cost of your time. It also doesn’t take into account the disposal of used oil. Many municipalities charge for oil disposal, and dumping it down the storm drain can earn you a nice hefty fine if you get caught.

7. Electrical work

Let’s get one thing out of the way immediately: In many municipalities, it’s flat-out illegal to monkey around with your home’s wiring yourself. Many building departments require that you get a permit, hire a licensed electrician and get an inspection if you want any electrical work done. If that doesn’t scare you off, how about the safety risks? “You usually don’t get a second chance with electricity,” says Michael Johnston, executive director of standards and safety for the National Electrical Contractors Association. “It’s not a job for a handyman.”

Even if you think you know your way around wires and circuits, you could get a nasty shock or even electrocute yourself. Faulty electrical work can also cause fires, and Johnston says you run the risk that your homeowner’s insurance company will deny your claim if the fire stemmed from work that wasn’t permitted or inspected.

6. Tax preparation

Yes, there are software programs out there that make doing your taxes as simple as plugging in numbers, but these tools have their limits. Even if you have a fairly simple tax status and don’t make mistakes with the software, you could be missing out on money that’s legitimately yours if you don’t claim it. “Sometimes there are deductions and credits a software program might not point out,” says Michael Eixon, director for planning and wealth management at Carl Domino Inc. in Palm Beach, Fla.

If you’re self-employed, own multiple properties, or have investments or different sources of income, sorting out all the details yourself can get really complicated. In addition, it’s virtually guaranteed that at least some part of the tax code will change each year, says Eixon.

So what happens if you decide to muddle through it and make a mistake? “You could owe back taxes, penalties and interest. There are some significant consequences,” says Eixon. If the IRS comes calling, you could be hit with a whopping bill. And if you can’t pay it all back at once, plan on shelling out an additional 7% in interest for the privilege of setting up a payment plan. What’s more, your tax disparities could trigger the IRS to audit you, and nobody wants to deal with that hassle.

5. Pricing heirlooms

There’s a reason TV programs like Antiques Roadshow are so riveting to watch: Most of us don’t have the slightest idea how much our old junk is worth. Slap a “50 cents” sticker on the wrong item at your great aunt Bertha’s estate sale, and you could be letting a neighbor walk off with the equivalent of a used car — or more.

Earlier this year, it was reported that a garage-sale shopper who picked up a box of old pictures had actually purchased long-lost photos taken by famous photographer Ansel Adams worth up to $200 million. On the flip side, what if you were counting on your grandmother’s ring to pay off your mortgage at retirement, only to find out after you’ve said goodbye to your job that the bauble is worth a tiny fraction of what you imagined? Both are very common outcomes when people try to guess how much their heirlooms are worth, says Patti Geolat, CEO of Geolat and Associates, a Dallas-based appraisal company.

“Typically, people make a lot of assumptions for any kind of an heirloom, whether it’s jewelry or antique furniture,” says Geolat. “If it’s old, it must be valuable,” is one common myth, she says. Another mistake a lot of people make is dividing up a set of something, such as jewelry or furniture, among family members. Sets are worth more when they’re intact, Geolat advises, so don’t break them up.

On a related note, if you inherit something like a grandfather clock or a baby grand, don’t attempt to move it to its new home by yourself. While specialty movers don’t come cheap, there’s a reason for that, explains Michael Feygin, owner of Amedeus Pianos in New York City. “The damage [the piece could sustain] costs more to fix than a new one costs to buy,” he says of botched piano-moving attempts. “We have special equipment and trained people.”

4. Representing yourself in court

Yes, we all love our Law & Order marathons. But if you ever have a brush with the law that’s more serious than fighting a traffic ticket, pony up for an attorney. “In general, real, everyday criminal trials are not like the ones on Law & Order or CSI. The way things unfold in court on TV doesn’t conform with the rules of procedure,” says Gary Dean Farmer, Jr., an attorney at Perlet & Shiner, P.A. in West Palm Beach, Fla.

If you represent yourself, evidence that was improperly gathered could be used against you, whereas an attorney would argue for it to be thrown out. If you don’t know what you’re doing, you could miss a deadline for filing any of the array of documents a criminal or civil case includes. If you’re being prosecuted or sued, the other party is sure to have legal representation, so you’re essentially fighting with a hand tied behind your back.

“The law is very, very complicated,” says Farmer. “I think you’re putting your rights at risk. If you get a misdemeanor or felony on your record, that will affect you for the rest of your life.” Remember, many lawyers will give you a free initial consultation, and if you meet certain income requirements, you may be eligible for a public defender.

3. Tree removal

The folks at DIY Chatroom know what they’re talking about, so when they say a full-grown tree is too big a job to tackle on your own, take heed. “Any tree over 5 inches in diameter has the potential to kill you if it hits you,” says Peter Gerstenberger, senior adviser for safety, compliance and standards for the Tree Care Industry Association. “Tree removal is an extremely tricky proposition,” he says.

Even if a tree looks fine from the outside, there could be weak spots or rot on the inside that could make the tree fall in an unexpected direction or before you’re ready for it to come down. Cutting into a tree to bring it down is far more precise than just whaling away at it with a chainsaw. It’s a carefully calculated physics equation taking into account the height of the tree (which is difficult to judge from the ground), wind speed at the tree’s top, any additional leverage needed and the condition of the trunk itself.

“A typical backyard hardwood tree weighs 50 to 60 pounds per cubic foot,” says Gerstenberger. “It’s an extreme amount of weight in the air. It’s really not a good idea to approach something that hazardous with minimal knowledge of how to control its fall.” Make a mistake, and your tree could land on a bystander, vehicle, house or electrical wire, any of which could lead to financial consequences far above the cost of hiring a pro to do the job.

2. Formal or large printing jobs

If you’re printing anything more complicated than a handful of copies, spare your home printer. A professional — whether a mom-and-pop print shop or a big office-supply chain — can help you do everything from formatting your files properly to proofreading spelling and aligning margins. You wouldn’t want to ruin a batch of pricey card stock because you notice after you finish printing that the right side of the words fall off the page or the name of the venue is misspelled.

“When you’re doing it yourself and you’re rushing and multitasking, and then you have to reprint it because you made a mistake, then you’re really inefficient,” says Jay Eisenberg, senior director of merchandising and marketing for Office Depot. “You’d be better served going to a professional printer.”

According to Eisenberg, black and white copies at Office Depot can be as little as three cents apiece for large orders. Printer ink is notoriously pricey, so depending on the brand of your home printer and how much your cartridges cost, that could be a great deal cheaper than the DIY route, not even counting the wear and tear on your machine or the price of the paper. Professionals also have access to goodies most of us don’t at home, such as high-quality copiers, metallic inks and foil finishing

1. Getting rid of bugs

Yes, pests are a pest, but it’s a bad idea to try to rid your house of them on your own, says Jim Fredericks, director of technical services for the National Pest Management Association. DIY pesticide application could be ineffective at best, or harmful at worst if you make a mistake applying the stuff. In 2003, San Diego homeowners literally blew up their house by setting off bug “bombs” improperly.

“If products are mixed improperly, they may not work, or they could be harmful if they’re applied to the wrong places,” says Fredericks. There’s also a chance that a layperson could misidentify the bug in question and either waste money applying a pesticide that wouldn’t kill them or miss the source of the infestation (bugs don’t always nest where you see them). Some insects, like pharaoh ants, will scatter and relocate to multiple locations in your house if you disturb their habitat without killing them all. You could also make your kids or your pets sick if you don’t follow application directions properly, says Fredericks. So why risk it?