Editing Aztec Code (section)

=== Padding ===
After bit stuffing, the data string is padded to the next codeword boundary by appending 1 bit.  If this would result in a code word of all ones, the last bit is changed to zero (and will be ignored by the decoder as a bit-stuffing bit).  On decoding, the padding bits may be decoded as shift and latch codes, but that will not affect the message content.  The reader must accept and ignore a partial code at the end of the message, as long as it is all-ones.

Additionally, if the total number of data bits available in the symbol is not a multiple of the codeword size, the data string is prefixed with an appropriate number of 0 bits to occupy the extra space.  These bits are not included in the check word computation.