Soft vs hard declines
Soft declines (e.g. 51 insufficient funds, 1A/65 SCA required, 91 issuer unavailable) can succeed later or with 3D Secure. Hard declines (04, 07, 14, 41, 43, 54, 57, R0/R1) will not succeed on retry — card networks may fine merchants for excessive retries on them.
All codes
00 01 03 04 05 06 07 12 13 14 15 19 30 41 43 46 51 54 55 57 58 59 61 62 63 65 1A 70 75 78 82 85 91 93 94 96 N7 R0 R1 R3 generic_decline insufficient_funds do_not_honor authentication_required card_velocity_exceeded transaction_not_allowed pickup_card fraudulent