Mailing a letter? You're going to have to fork over an extra nickel for that stamp.

According to The Associated Press, a first-class Forever stamp now costs 55 cents – a 10 percent hike from the previous price.

The change, which went into effect Sunday, is "the biggest price increase by total cents" ever for the U.S. Postal Service, the AP reported.

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Shipping rates for packages also have increased. Sending a small flat-rate box now costs $7.90, up from $7.20. Meanwhile, the price of shipping a medium flat-rate box rose from $13.65 to $14.35. The rate for sending a large flat-rate box shot up, as well, rising from $18.90 to $19.95.

Looking for more shipping rates? Click here to see the complete price list on USPS.com.

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