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A credit limit is the maximum amount of credit that a financial institution or other lender will extend to a debtor for a particular line of credit (sometimes called a credit line, line of credit, or a tradeline). For example, it is the most that a credit card company will allow a card holder to take out at once on a card.
This limit is based on a variety of factors ranging from an individual's ability to make interest payments, an organization's cashflow and/or ability to repay the credit card debt and is an obligation of the consumer to pay just like all other parts of the balance.
Maxed out 
A line of credit that has reached or exceeded its limit is said to be maxed out. While the line of credit is maxed out, it cannot be used for any further activity unless the consumer pays off at least some of the debt to enable it to fall below the limit, the creditor agrees to extend the limit, or the creditor allows one or more additional purchases with the charging of an over-the-limit fee.