Understand totals, included tax and precision
Total Amount is the whole recorded expense. Included Tax Amount records tax already inside that total; it is not an extra charge added by the form.
Numerical example
| Recorded field | Value |
|---|---|
| Total Amount | GBP 120.00 |
| Included Tax Amount | GBP 20.00 |
| Informational net by subtraction | GBP 100.00 |
| Initial Amount Due | GBP 120.00 |
The current journal builder debits the selected expense account for 120 and credits the applicable payable for 120. It does not post a separate recoverable-tax line for the 20. The informational subtraction above is arithmetic, not an implemented tax recovery calculation.
Rules and limits
Included tax is non-negative; omitted create tax becomes zero. The reviewed code does not enforce every desirable tax relationship, including a full tax-scheme calculation or complete tax-versus-total consistency policy. Review accurate source evidence rather than relying only on form acceptance.
Included tax is create-only in the current request/form workflow. Edit hides it, UpdateExpenseRequest has no tax field and the mapper preserves it. Changing total later does not recompute tax, so inspect whether the retained tax remains correct. The current UI has no direct “edit tax” procedure.
Amounts are stored with four decimal places, while many tables format to two. The browser uses ordinary numeric form values rather than Charity's exact-decimal transport approach. Do not assume its two-decimal presentation proves an exact minor-unit validation policy.
Examples and recovery
| Situation | Correct review |
|---|---|
| Tax included in total | Enter gross total and the included portion once |
| No included tax supplied | Stored zero, not a calculated tax rate |
| Total changed from 120 to 150 in draft | Due/approval recalculated for amount change; included tax remains as originally saved |
| Wrong included tax before posting | Escalate for approved correction; current edit cannot change it |
| Tax-recoverable treatment needed | Finance assesses the separate approved accounting process; do not assume split tax posting |
Do not invent statutory treatment from category, currency or the Included Tax label. The guide documents current software behaviour, not country-specific tax advice.