Standard and Poor’s ratings for long-term issuer credit are an assessment of a company’s creditworthiness, which means a company's ability to pay back its debts over a period lasting longer than a year. The score is based on a company's overall financial situation, including the amount of debt a company has, its payment history and its revenue. Each company may have a unique financial situation, which is why the S&P ratings scale allows the nuance of adding a plus- or minus-sign to each rating.