Prorated means an amount has been divided in proportion to a measured share, so a party carries only the part attributable to its portion of the whole. The measure is usually elapsed time, days in a month or months in a year, but it can as easily be units consumed, floor area or an ownership interest. A prorated figure is the full amount multiplied by that share, and the underlying rate does not change.
How to Calculate a Prorated Amount
One formula covers every case. The prorated amount is the full amount multiplied by the share of the measure, where the share is the part attributable to the party divided by the whole measure. The measure has to be named before the arithmetic starts: days, units, square feet or shares, whichever the agreement or the rule actually uses.
Say a firm agrees a flat monthly fee and the engagement starts partway through the month. The measure is days, the share is the days actually served, and the fee for that first month is the monthly fee times that share.
Monthly fee 3,000
Days in the month 30
Days served, the 12th to the 30th 19
Prorated fee 3,000 x 19 / 30 1,900
Daily rate 3,000 / 30 100
Check 100 x 19 1,900Two conventions decide the answer before the arithmetic does. A month can be counted by its actual days or by a standard month of fixed length, and the first day of service can be counted or left out. Both are defensible, and an engagement letter that leaves them unstated can bill the same situation two ways in two years.
Prorate, Prorated, Proration, and Pro Rata
These are one idea in four surface forms. To prorate is the verb, the act of dividing the amount. Prorated is the adjective for the result. Proration is the noun for the process. Pro rata is the Latin form, and it is the phrasing the statutes and the professional literature reach for, whether the share is an ownership interest, a claim or a stretch of time, as in a shareholder’s pro rata share of a corporation’s items.
Where Proration Shows Up in a Firm’s Work
Partial-period billing is the everyday case. An engagement that begins or ends mid-month, a subscription changed mid-cycle, a fee that follows a client for only part of the year: each is the formula above with days as the measure.
A prorated salary is that same formula on a pay period, the full salary times the share of the period actually worked. Payroll is also where the rule is written down rather than agreed. Under the Department of Labor’s salary basis regulation, an exempt employee must receive the full salary for any week in which the employee performs any work, without regard to the number of days or hours worked (eCFR, section 541.602(a)(1), Salary basis).
The same regulation then names the weeks where proration is allowed. An employer is not required to pay the full salary in the initial or terminal week of employment, and may instead pay a proportionate part of the full salary for the time actually worked in the first and last week of employment (eCFR, section 541.602(b)(6)). Prorating an exempt salary for a partial week in between is a different act. The same section permits it only in the listed exceptions, one of which is a week in which the employee takes unpaid leave under the Family and Medical Leave Act (eCFR, section 541.602(b)(7)). Outside them, the exemption itself is what is at risk.
Prepaid and accrued amounts are the third case, and the split at the close is only the arithmetic. Which period an item belongs to is a separate question, answered by the recognition tests in accrual accounting, and proration divides the amount once that question is settled.
Where Tax Law Prorates, and Where It Refuses
Tax law prorates by days where a share of a period is genuinely divisible. Each S corporation shareholder’s pro rata share of any item for a taxable year is the sum of the amounts found by assigning an equal portion of that item to each day of the taxable year, then dividing that portion pro rata among the shares outstanding on such day (26 U.S.C. 1377(a)(1)). Where a shareholder terminates the shareholder’s interest in the corporation during the year and all affected shareholders and the corporation agree, that day count is applied to the affected shareholders as if the taxable year consisted of two taxable years, the first ending on the date of the termination (26 U.S.C. 1377(a)(2)). What passes through to a shareholder, and who may elect S status at all, is in C corp vs S corp.
A short taxable year is the case where the proration lands somewhere other than where it looks. A return for a period of less than 12 months is required in either of two circumstances: when a taxpayer, with the approval of the Secretary, changes its annual accounting period, and when a taxpayer is in existence during only part of what would otherwise be its taxable year (26 U.S.C. 443(a)).
On the change of an annual accounting period, taxable income for the short period is placed on an annual basis by multiplying the modified taxable income for that period by 12 and dividing the result by the number of months in the short period, and the tax is then the same part of the tax computed on that annual basis as the number of months in the short period is of 12 months (26 U.S.C. 443(b)(1)). Income is scaled up to a full year first, and only the tax is split by months. That is the general rule, and a taxpayer that applies for the exception, and establishes its taxable income for the 12-month period the statute defines, has the short period tax reduced to the greater of two amounts, one scaled from the tax on that 12-month period and one computed on the short period’s own modified taxable income (26 U.S.C. 443(b)(2)).
Depreciation is the clearest refusal. Rather than count days from the date an asset is placed in service, the applicable convention is by default the half-year convention, which treats all property placed in service during a taxable year as placed in service on the mid-point of that year (26 U.S.C. 168(d)(1) and 168(d)(4)(A)). Nonresidential real property, residential rental property and railroad grading or tunnel bore take the mid-month convention instead (26 U.S.C. 168(d)(2)), and where that convention lands inside a building’s depreciation schedule is worked through in commercial real estate accounting.
The refusal goes further when purchases bunch at the end of the year. If the aggregate bases of property placed in service during the last 3 months of the taxable year exceed 40 percent of the aggregate bases of property placed in service during that year, the mid-quarter convention generally applies to the rest of that year’s property, and nonresidential real property, residential rental property and railroad grading or tunnel bore, along with any other property placed in service and disposed of in the same year, are not taken into account at all, neither in the test nor in the result (26 U.S.C. 168(d)(3)).
What Prorated Is Not
Apportioned is the state tax term, and it divides a different thing. Apportionment splits a multistate business’s income among the states that may tax it, using a formula built on factors such as sales, property and payroll, so the question it answers is which state gets the income rather than what share of a period an amount belongs to.
Amortized spreads a cost across periods by a schedule rather than by a share of a measure. A prorated amount answers what portion of one period’s charge a party owes. An amortized amount answers how a single cost already incurred is written off over the periods that follow it.
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