The 20k/500k note trap (and the change-swap that follows)

The 20,000 VND (~$0.76) note and the 500,000 VND (~$19) note are both blue-toned, and mixing them up is expensive in exactly one direction — a single swap costs you 480,000 VND (~$18).

The play:

1. Learn the lookalike pairs: 20k/500k (both blue) and 10k/200k (both brownish — the green 100k is the odd one out). Keep denominations in separate pockets so you never pay blind.
2. Count large notes aloud as you hand them over, and watch the exchange. The change-swap pattern: you paid with 500k, you’re shown a 20k and told that’s what you gave — or there’s suddenly “no change.”
3. Break big bills at convenience stores and pay exact where possible. Exact change — or a cashless Grab ride — removes the entire class of dispute.
4. Check the 200k and 500k notes that come back as change: feel the polymer texture, hold the watermark to the light. Counterfeits are rare but documented, mostly passed as change in small shops and taxis. A bank teller will verify a suspect note, and banks exchange genuine ones at no charge.

Price anchor: as of mid-2026, keep 20,000, 50,000, and 100,000 VND notes as your working cash and treat every 500,000 VND note like the ~$19 it is.

Verified: sources (2024–2026), 2026-07.