Projects / Cross-System VAT Calculation
Cross-System VAT Calculation
Two systems held different parts of one tax answer. The automation joins them, applies one calculation and returns a repeatable result without a hand-built spreadsheet.
One answer, split across two systems
Neither system was wrong or incomplete on its own terms. Each simply knew a different part of the calculation. Producing VAT for an Italian customer meant exporting from both, filtering both and manually building the columns that allowed the values to meet.
The work repeated for every customer and every cycle. A formula error or a copied value could alter the result, while the spreadsheet itself had to be rebuilt as part of the job.
The calculation was one process in the business and two unrelated processes in the software.
The join became part of the system
- 01Collect
Pull the required records from both source systems.
- 02Reconcile
Bring the two structures into one controlled calculation.
- 03Calculate
Apply the same rules in the same order for every customer.
- 04Return
Produce the final value without an intermediate hand-built sheet.
The important design choice is determinism. The same inputs take the same path and produce the same output, so the result can be repeated instead of reconstructed from someone’s clicks.
The manual cycle removed
- customers in the process
- ~11
- manual time per customer
- ~25 min
- manual time per full cycle
- ~4 h 35 min
The frequency of that cycle is deliberately not converted into an annual claim because it has not been confirmed. The defensible result is the complete manual block removed from each cycle.
Why repeatability matters here
For tax work, speed is useful but consistency is the stronger property. A repeatable calculation can be rerun on the same inputs, compared between cycles and inspected when a source changes. A manually assembled spreadsheet hides part of that history in the act of building it.
This project turns reconciliation from a personal procedure into an explicit system boundary: two sources enter, one answer leaves.
Visibility
This is a professional internal project. Client names, source-system names, tax records, formulas and production data remain private. The public description stays at the level of the data problem, process shape and verified time cost.