Late fees are governed by contract. If the agreement of sale or the credit agreement provides that creditors may charge late fees, they may do so starting whenever they are allowed under the agreement's terms. For example, a credit card or lease can provide that a late fee is levied as soon as a payment is late under the agreement's terms. Historically, there has been no law restricting when creditors can impose late fees. It's possible that some of the new credit/financial regulatory laws may require credit card companies, *going forward,* to allow more of a grace period before charging late fees, but even if that is part of the new package or regulatory scheme, it will only be on a going forward basis (so it won't affect previously levied late fees); will only affect creditors specifically covered under the law (and no others); and will be reflected in the new terms they provide.