Audit a quote by writing its units

These are invented units and rates. The model deducts a percentage from the destination gross amount. A fee charged on top, a fixed fee or a provider spread requires a different comparison.

WORKED EXAMPLE
Direct quote | 1 SRC = 1.25 DEST | Rate has units DEST per SRC.
Convert 100 SRC | 100 SRC × 1.25 DEST/SRC = 125 DEST | Source units cancel.
Deduct 2% | 125 × 0.02 = 2.50 DEST | Net received: 122.50 DEST.
Check inverse quote | 1 DEST = 0.8 SRC; 100 ÷ 0.8 = 125 DEST | The inverse must produce the same gross.

YOUR OWN PLAN
Quote source and timestamp: ___
Source currency: ___
Destination currency: ___
Quote written as 1 source = ___ destination
Source amount: ___
Gross destination = source × rate: ___
Fee convention: ___
Deducted percentage / amount: ___
Net destination: ___
Other fixed fees / spread outside this model: ___

Method: https://wanderaether.com/guides/exchange-rate-direction.html