How should shared expenses be split across my companies?

The short answer is to pick a defensible allocation method, document it, and apply it the same way every month. Arbitrary or improvised splitting is the fastest way to make every entity’s financials meaningless.

When you run multiple companies that share costs, such as a single office, shared software, a controller who works across entities, or ownership time that benefits multiple businesses, those expenses need to land on the books of each entity in proportion to the benefit received. The goal is for each entity’s profit and loss statement to reflect what that entity actually costs to run.

Common allocation bases include revenue, headcount, square footage, and actual usage. Revenue works well for costs that correlate with business volume. Headcount fits expenses that scale with people, like HR software or benefits administration. Square footage applies to shared space and utilities. Usage-based tracking works when you can measure it directly, such as time tracking for employees who work across entities.

The allocation method should make sense for the expense. Splitting rent by square footage occupied is logical. Splitting accounting software by revenue is not. Match the method to how the expense is actually consumed.

Document your allocation methodology once, in writing, and keep it on file. Specify which expenses get allocated, which method applies to each category, and how often the allocation percentages get updated. Some owners recalculate quarterly based on trailing revenue or headcount. Others set annual percentages and stick with them unless the business changes materially.

Apply your methodology consistently every close period. The discipline is monthly, not improvised. When you allocate shared expenses the same way month after month, the resulting financials tell you something real about each entity’s performance. When you guess or round or push costs wherever convenient, you lose the ability to see which entity actually makes money.

The paper trail matters. Lenders, investors, and tax professionals will ask how costs are allocated. If your answer is “we just split it roughly,” expect follow-up questions or discounted confidence in your numbers. A written policy applied consistently satisfies those questions before they become problems.

Arbitrary allocation also affects decisions. If one entity appears more profitable because it carries less than its fair share of overhead, you might invest in the wrong business or miss that another entity is quietly underperforming. Getting the allocation right means your financials support better decisions.

For businesses with the complexity of multiple entities and shared costs, managed accounting provides the structure to handle these allocations correctly each month, with proper documentation and review. This is exactly the kind of work where a Maui-based accounting company with multi-entity experience can bring genuine clarity to what would otherwise be a guessing game.

If your current books are unclear about how costs flow between entities, or you have no documented allocation policy, reach out to schedule a consultation. Getting this right simplifies everything else.