Cost Allocation Plan Calculator: Direct, Step-Down, Double Step-Down and Reciprocal Methods

The method

A central service cost allocation plan spreads the cost of internal services, such as IT, finance and facilities, to the departments that use them. Each service gets an allocation base that tracks use: devices for IT, transactions processed for finance, square feet for facilities. GFOA's guidance gives the same examples and asks only that the base "reasonably approximate the proportional share of service received." 2 CFR 200 Appendix V requires a plan to describe its method but does not prescribe one.

The complication is that central services serve each other. IT occupies Facilities space, and Finance processes IT's invoices. The four methods differ only in how they treat that cross-support:

The reciprocal method finds each service's full cost, meaning its own cost plus the support it receives, by solving the simultaneous equations

full cost of service s = own cost of s + Σ (share of service t used by s) × full cost of t

and then allocates each full cost by every operating department's share of use. At the defaults, $8,000,000 of central cost becomes full costs of $3,579,362 for IT, $3,167,735 for Finance and $2,469,571 for Facilities. The workbook solves the three equations with Cramer's rule in plain cells, so it needs no iterative calculation and no matrix functions. It also checks the answer by plugging it back into the equations.

The worked city has three central services and four operating departments: police, parks, development services, and a water utility run as an enterprise fund. The utility uses a lot of IT (SCADA, billing) and most of Finance's transactions, but very little city floor space because it has its own plant.

This spreadsheet is the form above, and every allocation on this page is a formula in it. Your own version could become the plan your departments update with their device counts and square footage each budget season, or an API that feeds the overhead charges straight into your budget system.

Which cost allocation method is most accurate: direct, step-down or reciprocal?

The reciprocal method is exact. The others approximate it, and the direct method, the one most often picked for simplicity, is furthest off for the department that matters most here. At the defaults it understates the water utility's overhead by $156,921. That overhead lands on the general fund instead, so taxpayers end up subsidising ratepayers.

The mechanism: Facilities spends part of its cost housing IT's servers and staff. The direct method spreads that Facilities cost by floor space, so it lands mostly on police, the biggest occupant. The reciprocal method follows it through IT to the departments IT actually serves, and the water utility is IT's largest user.

The gap grows with cross-support. In the workbook's own tests, raising IT's floor space from 22,000 to 200,000 square feet takes the direct method's understatement of the water utility from $156,921 to $538,578. The calculator shows the least operating use of any service, 77.90% here for Facilities, so you can see how much cross-support you are dealing with.

Does the order of departments matter in a step-down allocation?

Yes. Same costs, same usage counts, and the water utility's charge swings by $410,371 depending only on which service you close first. Single step-down gives the utility anywhere from $2,968,750 to $3,379,122 across the six possible sequences.

The usual rule of thumb is to allocate first the service that serves the other services most. Here that is Facilities (sequence 5), and it gives the highest water charge of all six: $123,258 above the reciprocal answer. The rule is a heuristic for reducing ignored cross-support, not a guarantee of accuracy, and a utility rate consultant can always pick the sequence that suits their client.

The double step-down narrows the swing from $410,371 to $51,659. That is why most municipal plans use it. Long Beach's full cost plan, for example, says it recognises "the cross support provided between central service departments". If you run any step-down, publish the sequence and keep it stable from year to year. A sequence that changes when the answer changes is the first thing an auditor or a ratepayer's lawyer will look for.

Does a double step-down allocate overhead twice?

No. Every dollar is allocated exactly once, and the workbook proves it: all four methods allocate exactly $8,000,000, every reconciliation reads zero, and all twelve step-down variants reconcile too. The "allocated twice" objection, raised in 2026 public comment on Sebastopol's cost allocation plan, mistakes the second step for a second charge.

The first step sends each service's own cost to everyone who uses it, other services included. At the defaults, $1,065,688 lands on other central services rather than on operating departments. The second step allocates only that $1,065,688 again, closing each service in sequence so nothing comes back. The first step plus the second step is still $8,000,000.

Where the confusion comes from: under the reciprocal method the full costs of the three services add up to $9,216,668, which is more than the $8,000,000 budget. That total counts the cross-support at both ends, but only $8,000,000 ever reaches an operating department. A full cost is a measure of what a service consumes, not a charge.

The legitimate questions about a cost allocation plan are its bases and its documentation, not the step count. That means asking whether square feet, devices and transactions are real, auditable counts, and whether they reflect who actually uses each service.

How much general fund overhead can a city charge its water utility?

The defensible answer is the utility's share of central services by actual use. Here that is $3,255,863 exactly, or $3,276,308 under the double step-down this city uses. The $20,444 between them is the approximation error of the method, not overhead the utility didn't use.

Charging too little is a problem as well as charging too much. The direct method's $3,098,943 leaves $156,921 a year of utility overhead on the general fund. In California, Proposition 218 (Article XIII D) caps property-related fees at the cost of providing the service, so ratepayers can challenge an inflated overhead transfer. A charge built on documented usage counts and a published method is what holds up.

Two practical points:

• The overhead charge feeds the rate study. The utility's share of city overhead is one line in its revenue requirement. If it is wrong, every customer class's rate built on it is wrong too.
• Use the full cost plan for the utility, the federal plan for grants. A full cost plan allocates everything. A 2 CFR 200 plan must exclude the general costs of government under 2 CFR 200.444, such as the chief executive's office and the city council. Many cities run both from the same model.

This is not legal advice; a rate challenge turns on the facts and the documentation.

What this calculator does not do

Stated plainly, so you know when to reach for a full cost allocation plan model:

• Three central services, one allocation base each. Real plans often split a department into functions (payroll, accounts payable, budget), each with its own base.
• Allocated central services only. Billed services and internal service funds charged per use, such as fleet and self-insurance, are not modelled.
• A full cost plan, not a 2 CFR 200 plan. It allocates every cost you enter. To prepare a federal plan, remove unallowable general government costs from the service costs before you enter them.
• One form of double step-down. Here the first step is order-free and the second step runs in the chosen sequence. Some consultants also sequence the first step, which gives slightly different figures.
• Four operating departments, one year. No carry-forward or roll-forward of prior-year over- and under-recoveries, and no actual-versus-budget true-up.
• Drivers as given. The model does not test whether your counts are accurate. That is what an auditor will test first.

Sources

• 2 CFR 200 Appendix V, State/Local Governmentwide Central Service Cost Allocation Plans
• 2 CFR 200.444, General costs of government
• GFOA: Indirect Cost Allocation
• City of Long Beach FY 2021-22 Full Cost Plan
• Washington State Auditor: Cost Allocation
• City of Sebastopol, 2026 public comment on the cost allocation model