Fees as Percentages: Line Items Calculated from a Base Value
What this is about
Many professional fee scales don't work with unit prices but with shares of a total value: the German HOAI splits an architect's fee into service phases (phase 5 = 25 %, phase 8 = 32 % …), the Swiss SIA regulations use partial services in percent, and project management per AHO follows the same pattern.
That's exactly what the dynamic item “Share of Base Value” is for: store the total once per document and enter just the percentage per line – GrandTotal does the math.
How it works
Insert a dynamic item and pick “Share of Base Value”. If the document has no base value yet, GrandTotal asks for it right away – once per invoice or estimate. From then on the percentage is simply the item's quantity:
The unit price shows the value of one percent – so each line reads like a verifiable calculation: 25 % × 1,000.00 = 25,000.00.
The base value
The base value lives in the document info and applies to all percentage items of the invoice. When it changes – say, an updated cost calculation – every item recalculates instantly. The field even accepts formulas: 350000*1.19 is evaluated as you leave the field.
The base value field only appears once the document contains at least one “Share of Base Value” item.
Example: a fee invoice per HOAI
The derivation – chargeable costs, fee zone, rate, total fee – goes into the invoice's introduction as usual. The total fee becomes the base value; each commissioned service phase becomes one item with its official percentage as quantity:
| Item | Quantity | Amount |
|---|---|---|
| Phase 3 · Design planning | 15 % | 15,000.00 |
| Phase 5 · Execution planning | 25 % | 25,000.00 |
| Phase 8 · Site supervision | 32 % | 32,000.00 |
Not just for architects
The “total × rate” pattern appears in many fee scales: SIA 102/103/108 in Switzerland, AHO project management, the tenth-rates of German tax consultants or lawyer fees per RVG. Percentage items work in estimates too; converting to an invoice carries the base value along.
At a Glance
Percentage = quantity
Enter just the rate per item – GrandTotal calculates the amount.
One base value per document
Stored in the document info, requested when you pick the item type.
Live recalculation
Change the base value – all percentage items update instantly.
Formulas in the field
Entries like 350000*1.19 are calculated on the spot.
Estimates too
Converting to an invoice carries the base value along.