AI costing prompts · By role
AI costing prompts for the cost and management accountant
You work where costing is actually done: cost pools, drivers, time equations, the allocations everyone else takes on trust. The detail is the job, and it is also where a single bad assumption quietly distorts every downstream number. AI can help you build and test that detail faster, but only if it never fabricates a rate or a driver behind your back. These are the most technical prompts in the hub.
In short
Use AI as a meticulous junior who never tires of structure: defining cost pools, drafting time equations from your process steps, computing capacity cost rates, and stress-testing whether an allocation holds together. The prompts below go deep into the mechanics. Each forces the model to work only from your figures, to show every formula before any value, to reconcile back to the totals you supplied, and to label anything it was not given, so the technical work stays auditable.
What a cost accountant should and should not ask AI to do
AI is a fast and consistent partner for the structural mechanics of costing. It can organise a chart of cost pools, write a time equation from the activity components you describe, compute capacity cost rates and apply them, and check the internal consistency of an allocation: whether the driver units sum correctly, whether assigned cost reconciles to pool cost, whether two activities are quietly drawing on the same minute of capacity. It is also a good adversary, useful when you want someone to poke at a model you have built and surface the weak joints.
The line it must not cross is supplying inputs. A time-per-unit, a practical capacity, a driver volume, a department cost: these come from your data and your judgement, never from the model's sense of what is "typical." Ask it to estimate any of them and you get a number with the texture of fact and none of the substance, which is the worst kind in a cost model because it propagates silently. Keep the inputs and the allocation policy yours; let AI handle the assembly and the checking.
Three prompts to start with
1. Build cost pools and time equations
The technical core: turn process detail into a clean set of pools and equations. Builds on the build a TDABC model page.
You are a cost accounting assistant helping define cost pools and time equations for a TDABC model. Work only from the data I give you. Do not invent any times, rates or volumes. Show every formula before any value. Label anything missing as DATA MISSING with what you need. My data: - Resource groups and their total cost for the period: [paste] - The activities each group performs and the process steps in each activity: [paste] - The time drivers for each step (for example, base time plus added time per line item): [paste what I have] Steps: 1. Propose a clean set of cost pools mapped to my resource groups; do not merge or split without telling me. 2. For each activity, write the time equation from the step components I supplied, in the form base + (per-unit time x driver quantity). 3. Mark any step where I have not supplied a time component as DATA MISSING. 4. Show the structure of how cost will flow from pool to activity to object as formulas, with no values yet where data is missing. 5. State clearly what I must provide before any number can be computed.
2. Compute capacity cost rates and unused capacity
Get the rate right and the rest follows. See capacity cost.
You are helping a cost accountant compute capacity cost rates and unused capacity cost. Work only from the data I give you. Do not invent any figures. Show each formula before the value. If you cannot derive something, say so rather than estimate. My data: - Resource groups with total cost: [paste] - Theoretical capacity and practical capacity in minutes for each: [paste] - Minutes consumed by activities this period: [paste] Steps: 1. For each group, show the capacity cost rate as cost / practical capacity minutes, formula first. 2. State the basis you used to get from theoretical to practical capacity, using only what I gave you. 3. Compute used vs unused minutes and the cost of unused capacity, each as a formula. 4. Separate clearly: calculated from my data, assumed, and flagged for review. 5. Check that used cost plus unused cost equals total cost for each group and report any mismatch.
3. Stress-test an allocation
Find the weak joints before someone else does. Links to cost-to-serve.
You are acting as a critical reviewer of a cost allocation built by a cost accountant. Work only from the data I give you. Do not invent numbers. Your job is to find weaknesses, not to smooth them over. My data: - The allocation: pools, drivers, driver quantities, and cost assigned to each object: [paste] - The totals each level should reconcile to: [paste] Steps: 1. Check that assigned cost reconciles to pool cost and to the grand total; show each check as a formula and flag any gap. 2. Identify any object where one driver dominates the result and ask whether that driver is appropriate. 3. Flag any sign that two activities draw on the same capacity (double counting), citing the rows. 4. List the assumptions the allocation depends on and rank them by how much the result moves if each is wrong. 5. Separate what is a confirmed error from what is a question for me to judge.
The one rule
Work only from the data I give you. Do not invent any times, rates or volumes. Label anything missing as DATA MISSING and tell me what you need.
In a cost model a fabricated input does not stay put; it propagates through every allocation. For the full set of safeguards, read how to stop AI inventing your numbers.
The detail is right; is the design?
You can get the mechanics right and still be modelling the wrong thing if the cost pool structure or driver choice does not fit how the business actually consumes resources. That design judgement is what we bring: years of building TDABC models that reconcile to the ledger and survive scrutiny. If you want a second set of senior eyes on your model's design, not just its arithmetic, a health check is the place to start.