Short-term payday loans often have high interest rates

Short-term payday loans often have high interest rates. £400 borrowed for 28 days at 1737% APR means you would have to pay back £500 at the end of the month – so you pay £100 for the privilege of borrowing £400 for a month, and also have to repay the £400.

Source: Payday loans @ The Money Advice Service

Understanding the risks of short-term loans @ NI Direct
Excerpt: Payday loans are increasingly being used by some people as a short-term way of borrowing money. However, it is very important to understand fully the pros and cons of this method of borrowing. Often these loans have extremely high interest rates and there are risks if you fall behind with your repayments.
Payday loans @ The Money Advice Service
Excerpt: Normally you’ll be given up to a month to pay back the money you borrowed plus interest. Some lenders let you to choose the repayment period. The repayment, plus interest, is then taken directly from your bank account on the date you’ve agreed to pay back the loan.