A memory tag comprising a resonant circuit part and a non-volatile memory, the resonant circuit part being operable, in response to a reader signal received from a reader, to provide power to the memory, the tag being operable to read the memory and transmit data stored in the memory in response to the signal from the reader, wherein the data is stored in the memory in a plurality of data units, each data unit having an associated sequence number, the tag being operable to store the sequence number of the data unit to be transmitted in a register in the non-volatile memory, and when power is supplied to the memory, the data units are transmitted in sequence, the first data unit to be transmitted depending on the stored sequence number.