What is Applicable Convention?

Legal Definition
An applicable convention, as presented in 26 U.S.C. § 168(d) of the United States Internal Revenue Code, is an assumption about when property is placed into service. It is used to determine when property depreciation begins. The purpose of applicable conventions is to simplify depreciation because they do not require a taxpayer to prove to the IRS when every piece of depreciable property was placed into service.

There are three types of conventions. The first, the “half-year convention,” assumes that all property placed into service, or disposed of, during a taxable year was placed into service, or disposed of, at the midpoint of that year. (§ 168(d)(4)(A)) Section 168(d)(1) states that all taxpayers should use the half-year convention unless a different convention is specifically required by § 168(d)(2) or § 168(d)(3).

The second, the “mid-month convention,” assumes that all property placed into service, or disposed of, during any month was placed into service, or disposed of, at the midpoint of that month. (§ 168(d)(4)(B)) Section 168(d)(2) tells a taxpayer when it is appropriate to use the mid-month convention.

The third, the “mid-quarter convention,” assumes that all property placed into service, or disposed of, during any quarter of a taxable year was placed into service, or disposed of, at the midpoint of that quarter. (§ 168(d)(4)(C)) Section 168(d)(3) tells a taxpayer when it is appropriate to use the mid-quarter convention. Specifically, if a taxpayer buys a lot of depreciable assets in the last three months of the taxable year, the taxpayer will in some cases be forced to use the mid-quarter convention, resulting in an even smaller depreciation deduction in the first year as compared to the half-year convention.
-- Wikipedia
Legal Definition
An international agreement that clears up any linguistic concerns about words in a case.