Nudge Feature

The nudge feature lets you adjust a value by one cent ($0.01) at a time, while ensuring the Amount stays the same.

Why nudge exists

Currency calculations with rounding can produce ambiguous results. For example, at a 15% rate, a gross amount of 115.00 produces an Amount of 15.00. But 114.97 and $115.03 might produce the same Amount of 15.00, because both round to the same Amount.

This creates a range of gross amounts that all result in the same tax. The nudge feature lets you explore this range safely — you never accidentally “break” the calculation and change the Amount.

How it works

Each value has an upper and lower boundary calculated by the algorithm. Within these boundaries, the tax remains constant. The nudge buttons move the value up or down by one cent within these boundaries.

• ▲ (nudge up) — increases the value by one cent (up to the upper boundary)
• ▼ (nudge down) — decreases the value by one cent (down to the lower boundary)

When a boundary is reached, the corresponding button becomes disabled (dimmed and non-clickable).

Which fields can be nudged

Field	Nudgeable?	Reason
Before	✅ Yes	Before has calculated boundaries
After	✅ Yes	After has calculated boundaries
Amount	❌ No	Amount is a derived value, not directly adjustable

Example

At a 15% rate with an After value of 115.00:

• The algorithm calculates that any After value between 114.97 and 115.03 produces an Amount of 15.00
• Upper boundary: 115.03
• Lower boundary: 114.97
• You can nudge After down to 114.97 or up to 115.03

This is useful when you want a “round” number for one field without changing the Amount. For example, your invoice system might prefer a round Before amount while keeping the same Amount total.

The nudge toolbar

Located between the display fields and the keypad:

Element	Description
Active field label	Shows which field will be nudged (BEFORE or AFTER, uppercase). Changes when you tap a different display field.
▲ / ▼ buttons	Nudge up/down by 1 cent. Disabled at boundaries or when Amount is active.
Direction button (+ / −)	Toggles between additive and subtractive mode. See calculation direction.
Rate badge	“15%” shows the current rate. Tap to change it — see rates.

The nudge buttons, direction toggle, and rate badge are grouped at the right end of the toolbar.

Practical uses for nudging

1. Rounding to a nice number — Your system calculates After as 115.03, but you want to charge 115.00. Nudge After down by 3 cents. As long as you stay within bounds, the Amount stays the same.

2. Fixing a penny-off discrepancy — Sometimes rounding creates a 1-cent difference between systems. Nudge the value to match. all within the calculation’s valid boundaries.

3. Adjusting to a preferred price point — If you want an After value of 99.99 instead of 100.00, nudge down. The algorithm ensures the Amount calculation remains consistent.

How boundaries are calculated

The algorithm uses a boundary-finding approach:

1. Starting from the current value, it walks outward (up and down) one cent at a time.
2. At each step, it recalculates the Amount for that candidate value.
3. As long as the Amount stays the same, the boundary extends.
4. When the Amount changes, the boundary is set — the last value that still produced the same Amount.

This is done for both After and Before independently, then cross-checked for mathematical consistency (the “integrity check”). This ensures that nudging one field and then the other does not produce contradictory results.

Keyboard shortcuts

Shortcut	Action
ArrowLeft or Shift+H	Nudge active field down
ArrowRight or Shift+L	Nudge active field up
Shift+ArrowUp	Nudge active field up
Shift+ArrowDown	Nudge active field down

See the full keyboard shortcuts reference for more.