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If you're thinking about applying for Social Security benefits tied to your spouse's work history, then there are three rules you need to keep in mind before doing so.

1. You can't apply for them until your spouse has
The age limit to apply for spousal benefits is the same as it is for regular retirement benefits -- that is, you're eligible to begin receiving them at 62 years old. But there's a catch. That is, in order to qualify for spousal benefits, the working spouse must have already applied for their own.

For example, let's assume that you're 63 years old and are qualified to receive benefits based on your spouse's work history. If your spouse is 64 years old but hasn't yet applied for his or her own benefits, then you must generally wait until they do so before you're eligible to begin receiving yours.

There is one quasi-exception to this rule known as the "file and suspend" strategy. This allows your spouse to claim benefits but then immediately suspend their receipt. Doing so triggers your eligibility to receive benefits while preserving your spouse's right to accumulate delayed retirement credits.

2. Your age impacts the size of your benefits
Even though you have a four-year window to apply for spousal benefits -- that is, between the ages of 62 and 66 -- the age at which you apply for them within this period makes a difference when it comes to the size of your benefits.

If you wait until reaching your full retirement age -- which, at present, is 66 -- then you're entitled to 50% of your spouse's primary insurance amount. But if you apply before this, then you're penalized by a set amount for each month prior to full retirement.

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Here's how the Social Security Administration explains this:

A spouse can choose to retire as early as age 62, but doing so may result in a benefit as little as 32.5% of the worker's primary insurance amount. A spousal benefit is reduced 25/36 of 1% for each month before normal retirement age, up to 36 months. If the number of months exceeds 36, then the benefit is further reduced 5/12 of 1% per month.

3. You don't get delayed-retirement credits
If you qualify for Social Security benefits on your own earnings history but don't apply for them until you turn 70, you're rewarded for waiting with delayed-retirement credits. These can increase your monthly check by as much as 32%, or 8% for every year that you don't apply for them after reaching your full retirement age but before turning 70.

Unfortunately, the same isn't true of spousal benefits. That is, no matter how long you wait beyond full retirement age to apply, the size of your benefit is capped at 50% of your spouse's primary insurance amount.

Meanwhile, the age at which your spouse applies won't impact the size of your benefits. Let's say, for instance, that they wait until turning 70. While their benefits will be larger, yours will still be capped at 50% of their primary insurance amount.

The net result is that there's absolutely no reason to forgo your Social Security spousal benefits once you've reached your full retirement age.

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