You are sent advertisements for expensive items

Ads for flashy vehicles or unfamiliar health care services could be signs of fraudulent activity on your account, according to Payton. Scammers often charge big-ticket expenses to victims’ credit cards, which results in more direct mail and phone solicitations for those items.
Read about ways in which former identity thieves scammed people from right under their noses.
You are notified that your information has been compromised

Believe it or not, your employer might be one of the first to know if your information has been stolen. An identity thief with your tax file number or tax identification number and the name of your current employer might try to collect unemployment benefits in your name. Eventually, your employer or an unemployment agency will notice and let you know that something seems fishy. To protect yourself against fraud, avoid giving out your tax file number unnecessarily.
You receive statements for credit cards you don’t have

Receiving statements for credit cards you never signed up for that are full of charges you don’t recall and getting receipts for purchases you never made are major signs that someone has stolen your information. Identity thieves may use your information to make purchases in your name, upgrade existing accounts, or open new accounts. Unfortunately, you may not find this out until you receive the bill in the mail.