In law, filing is the act of submitting a document to the clerk of a court for the court's immediate consideration, for storage in the court's files, or both. Courts will not consider motions unless an appropriate memorandum or brief is filed before the appropriate deadline. Usually a filing fee is paid at the same time; such filing fees are one part of the variety of charges that are known as court costs.

Filing may also refer to submission of a form to a government agency, with or without an accompanying fee.

Filing fees are controversial because they impede access to justice. Although American litigants complain about fees all the time (for example, it costs $300 to file a document in court in Los Angeles), the American system is considered to be quite plaintiff-friendly by lawyers.

Many legal systems have filing fees for complaints that are proportional to the amount in controversy. That is, the bigger the damages, the bigger the fee!

Even when one seeks a waiver for grossly unfair fees, courts tend to waive only the amount in excess of the plaintiff's total assets, with the perverse result that just to initiate a meritorious case, an already severely injured or damaged plaintiff may have to go bankrupt.