You're nearly ready to claim Social Security. You already know when you want to receive your first check. Now you're just biding your time until you fill out your application.

But while you still have a bit to wait, it's worth taking a few preparatory steps to ensure the application process goes smoothly and that you don't accidentally short-change yourself. Start with the three things listed below.

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1. Understand how your claiming age affects your benefit

When you sign up determines the size of the check you qualify for, along with your income history from your working years. You can apply as early as age 62, but that's considered claiming early, and it carries a penalty of up to 30%.

If you want to avoid early claiming penalties, you have to wait until your full retirement age (FRA) to apply. That's 67 for most people today. You can also delay checks beyond your FRA, and they'll continue to grow until you qualify for your maximum benefit at 70.

The easiest way to know what sort of benefit you'll qualify for at every claiming age is to make a my Social Security account. There's a tool here that can show you your estimated benefit for every month between your 62nd and 70th birthdays.

If you didn't know how your age affects your benefits, you may want to rethink your claiming strategy. If you can afford to delay, and you expect to live into your 80s or beyond, you may get a larger lifetime benefit by waiting to sign up. If you have a short life expectancy, you might choose to sign up a few months earlier than you'd planned.

Make sure you're comfortable with your estimated benefit amount before you proceed. It's possible to withdraw your Social Security application after you've signed up, but this isn't always easy to do. It's much better to choose a claiming age you're happy with from the start.

2. Decide when you're going to apply

When you're going to apply and when you hope to start claiming checks are two different things. You can apply up to four months before you want to receive benefits, and it's often best to do so. This way, if there are any issues with your application, you'll have time to resolve them without them interfering with your financial plans.

Keep in mind that the government pays checks in the month after the month they're due, so if you want January to be your first month of benefits, you won't actually see a check until February -- possibly late February, depending on your birthday. So you'll need a plan to cover your expenses on your own until then.

Those who plan to apply as soon as they turn 62 should also be aware that you're not eligible for benefits until you're 62 for the entire month. The Social Security Administration (SSA) considers your birth month as your first month of eligibility if you were born on the first or the second of that month. Otherwise, you're not eligible until the month after your birth month, so you may have to push your application date back a bit longer than you intended.

3. Gather your documents

Not having the necessary documentation can slow your Social Security application, so it doesn't hurt to get the paperwork together ahead of time. If you're applying for retirement benefits, you'll need:

  • Your Social Security card or another record of your Social Security number
  • Your original birth certificate or other proof of your age
  • Proof of U.S. citizenship or lawful alien status
  • A copy of your U.S. military service papers if you served before 1968
  • A copy of your W-2 or self-employment tax returns from the last year

Photocopies are acceptable for all except your birth certificate and proof of U.S. citizenship or lawful alien status.

If you don't have all the documents you need, see if you can gather them on your own. You may need to contact other state or federal government agencies to do this.

Don't let missing documents halt your application altogether, though. If you're having trouble tracking down some information, the SSA might be able to help you.

You should also reach out to the SSA if you have any questions about your application. You can do this by phone or by scheduling an appointment with your local Social Security office.