It's a good idea to look through your credit report at least once yearly to make sure that everything looks good and that there haven't been any entries mistakenly added to it. The longer you wait to look at your report the harder it will be to fix anything that has been added to it incorrectly. In some cases even a wrong address or misspelled name can cause confusion when you're applying for credit such as a credit card or a home mortgage.
It happens quite commonly. You make all of your credit card payments on time but for one reason or another a late payment has been added to your credit report. You know that you have been good on your payments and that it is a mistake. Working through the credit card company you can get this removed from your credit report with a small amount of effort on your part and keep your credit history intact.
Any mistake that is sitting on your report will act as a black mark against you when you are applying for credit. The lender will take the credit report information as fact and once you have submitted your forms it's too late to change the information on your credit report for that application. This means that you may possibly be turned down for your loan, which will only end up adding another black strike against you on your credit history.
The other thing that you can run into is identity theft showing up on your report. If you see anything on your credit file that you never ordered or applied for, there's a good chance that you have become a victim of identity theft. This happens to seniors unfortunately quite often. The sooner you catch any sign of identity theft occurring the better off you'll be. Some people have had their clean credit history ruined by identity thieves and in some cases it has taken months to get everything resolved back to the way it should have been in the first place.
Remember to check your credit report at least once yearly. In most cases you'll see no problems showing up but in the rare case that you do, you'll be able to get it corrected before you apply for your next loan.