Thermal receipt paper — the glossy, curling kind most registers print — is a genuinely harder scanning case than standard printer paper, for reasons specific to how it's made.
Low contrast printing
Thermal printing produces text with lower contrast and finer, sometimes faded strokes compared to laser or inkjet printing, which makes edge detection and OCR both meaningfully harder.
The curl problem
Receipts naturally curl from the thermal printing roll, and that curve introduces exactly the kind of non-flat distortion that basic perspective dewarping doesn't fully correct — flattening the receipt by hand before scanning helps noticeably.
Fading over time
Thermal paper fades with heat and light exposure over weeks or months — scanning a receipt soon after purchase, rather than months later, meaningfully improves both visual quality and OCR accuracy.
Should you scan receipts immediately or is it fine to batch them later?
Scanning sooner is genuinely better given how quickly thermal paper can fade — for anyone tracking expenses seriously, scanning at time of purchase (or within days) avoids losing legibility to fading.