With so many tax-related computer programs out there, filing your own income taxes doesn’t have to be complicated. But not even the most sophisticated software can prevent people from making the kind of dumb mistakes—or from telling little lies—that raise a red flag with the Canada Revenue Association.

Here’s a look at common blunders that tend to trigger assessments or audits.

Extra zeros.

There’s a big difference between claiming $15,350 on meals and entertainment for business expenses and $1,530.

“Accounting firms received an email from CRA last week about taxpayers adding extra zeros, resulting in huge tax liabilities,” says Christian Stewart, certified general accountant and founder of North Vancouver’s Stewart & Associates. Be sure to triple-check your return before filing.

Fibbing about a pastime being a business.

“Taxpayers will often claim a hobby business on their tax return, reporting losses year after year,” Stewart says. “Common ones would be an artist who never sells a painting or a musician who gigs once a year but writes off auto, home office, and cell-phone expenses. This is a huge red flag.”

In other words, don’t give up your day job.

Not claiming tips.

If you work at an upscale spot that regularly draws lineups, don’t expect to get away with claiming you make $100 a week in tips for long.

“Tips are considered income, and service workers should keep detailed daily records of their tips,” says Caroline Battista, senior tax professional at H&R Block. “They add up more quickly than you think. The CRA expects tips for servers and waiters to be between 100 and 400 per cent of their income.”

Falsely describing marital status.

The CRA considers you and your partner common-law as soon as you’ve lived together for 12 consecutive months or have a child together, whichever comes first.

“People realize they may lose their federal and provincial benefits if they claim common-law or married instead of single,” Battista says. “When you both file from the same address [but you have stated you’re single], the CRA may determine you have falsely claimed your marital status, and this can result in costly penalties and repayment of credits received.”

Incorrectly deducting “charitable” donations.

Only receipts from registered Canadian charities qualify for the credit.

“Receipts from not-for-profit organizations do not count,” Battista says, “so make sure all of your receipts have a registered charity number on them.”

Claiming the cost of elective cosmetic surgery as a medical expense.

No, you cannot write off fees such as those for rhinoplasty, breast enhancement, or Botox that arise out of vanity.

“Taxpayers still think this is a write off,” Stewart says. “CRA often requests proof of receipts and will deny any cosmetic surgery unless that surgery is required as a result of disease or an accident and the like.”

Other tax deductions that tend to pique CRA’s interest are unusually high medical expenses or moving expenses. If they’re legit, be sure you have the documentation to prove it.

“You may have had some major dental work performed or one of your children got braces, making your expenses higher than in previous years,” Battista says. “The CRA may request receipts to support your claim so make sure you keep all of your receipts and paperwork in case they ask for it.”

Moving expenses are eligible for a tax credit if you have to relocate more than 40 kilometres for work or school; again, it’s crucial to keep any related papers and receipts.

If those costs aren’t legit, consider yourself warned.

