Even if you have a good relationship with your credit card company, its important to remember that its in business to turn a profit . That means there are a few practices it would rather not advertise for fear of losing money your money.

Below are five things it pays to know but that you probably wont hear about from your credit card company .

1. Your interest rate can go up without notice

The Credit Card Accountability Responsibility and Disclosure Act of 2009 more commonly known as the CARD Act was put in place to protect people from predatory credit card practices. One of the things it did was place rules around when and how credit card companies can raise interest rates.

For instance, credit card issuers are supposed to provide 45 days notice if they decide to raise your rate. If youve owned the card for less than a year, the card issuer cant raise your rate at all unless youre at least 60 days behind on payments and incur a penalty annual percentage rate.

However, there are instances when your credit card company can increase the interest rate on your card with no warning. For example, if you enjoyed a lower interest rate thanks to a promotion and the promotional period ends, the card company doesnt have to give you a heads-up that the rate is going back up. And if the Federal Reserve raises rates (as it recently did for the third time this year), your credit card rate can also go up without notice.

2. Your sign-up bonus might be taxable

One of the biggest incentives to apply for a new bank account or credit card is often the sign-up bonus. Just by becoming a new customer, you can earn extra cash, points or miles worth hundreds of dollars.

Even though we often think of these rewards as free money, they arent always. As it turns out, they might actually count as taxable income. It all depends on how you earn them.

The most well-known example of rewards being taxed is when Citibank sent a portion of its credit card customers (and the IRS) 1099 forms for the miles they earned as part of a checking account sign-up bonus in 2012. Usually, the IRS considers rewards points earned for spending money to be discounts rather than income. But because these Citi customers didnt have to spend any money to earn the points, the bonuses were considered cash gifts that had to be reported on their taxes.

3. They can snoop on your credit activity

Read through the fine print of your card contract (as if anyone does that) and youll likely find a universal default provision. This controversial practice allows your credit card issuer to regularly review your credit profile and keep tabs on any negative changes such as missed payments or high balances.

If it sees something it doesnt like, your issuer can raise your interest rate even if the negative item was related to another credit card or loan. So if you miss a payment on your auto loan or mortgage, you might end up paying more on your credit card balance as a result.

Card companies also perform periodic reviews of your account to make sure youre still meeting their standards well after you first opened it. Usually, these reviews happen every six to 12 months. The good news is they can work in your favor if your issuer likes what it sees, it might actually increase your credit limit.

4. Everything is negotiable

Wish your due date was on a different day? Your interest rate was lower? That late fee would get waived? Often, all you need to do is ask .

Credit card companies are in constant competition for your business. If you have a reasonable request and can show that youve been a good customer, your issuer will likely be willing to work with you.

However, dont bring unneeded scrutiny to your account if your track record is spotty. If youve missed a few payments or have been maxing out your card every month, the issuer might decide to lower your limit instead of granting your request.

5. You have more power than you think

Though all of the above practices are completely legal, there might be a time when you believe your credit card company is breaking the law. Fighting it might seem like a David vs. Goliath situation youd rather not get involved in. The truth is, you have a few strategies at your disposal.

According to Teel Lidow, a former product manager at LegalZoom who founded the startup Radvocate , credit card companies want to make it seem like its hard to take them to court. In fact, credit card agreements often try to force customers into a system of binding arbitration that prohibits them from going to court or joining a class-action lawsuit.

However, Lidow has found that simply knowing your rights under your service agreement and raising the topic of arbitration can get large companies to back down.

If youre not interested in taking things that far, you can enlist the help of the Consumer Financial Protection Bureau. If your card issuer gives you the run around when it comes to resolving an issue, you can file a complaint with the CFPB , said Lou Haverty, a certified financial analyst .

In many cases, [the credit card company] will fix the problem, Haverty said. At a minimum, they will respond directly to the complaint and give you a clear explanation of why they did what they did.