There is evidence - Petersen and Rajan (1997) - that suppliers have superior information on their clients capacity of repayment. However, Elliehausen and Wolken (1993) report that trade credit rates are frequently standardized. Why do not suppliers use their informational advantage to make the interest rate reflect the risk? This work shows that, if the demand for imputs is sufficiently inelastic, competition among banks leads the trade credit rate to be invariant and very close to banking rate. On the contrary, if the demand is sufficiently elastic, the trade credit rate is invariant and equal to zero, as usually occurs with suppliers credit with maturity until 10 days in USA.