When a mortgage refinances or the borrower prepays during the month, the prepayment measurement increases. Federal credit unions are also forbidden from charging prepayment penalties on loans. Prepayment uncertainty is an important concern with fully amortizing ABS. Investors in CMOs wish to be protected from prepayment risk as well as credit risk. Balloting materials may be sent via the United States Postal Service without prepayment of postage. The prepayment audit is a restricted audit of Input Tax Credits (ITCs). Prepayment penalties are still common, whilst the United States has discouraged their use. The fundamental purpose of a stamp is to indicate the prepayment of postage. Most aerograms have an imprinted stamp indicating the prepayment of postage. Prepayment of postage became compulsory on 1 March 1858. European CMBS issues typically have less prepayment protection. This coupon stream allocation is performed after prepayment tranching is complete. Victoria was the first to make prepayment by stamps compulsory in 1852. The MBS adds a third risk&colon; early redemption (prepayment). Hence the term "prepayment risk".