A purported variation of a contract of employment that is, or will be, transferred as part of a TUPE transfer is void under regulation 4(4) 'if the sole or principal reason for the variation is the transfer'. However, under regulation 4(5) a variation to the contract of employment of a transferring employee will not be void: • if the sole or principal reason for the variation is an economic, technical or organisational reason entailing changes in the workforce (ETO reason), provided that the employer and employee agree that variation, or • the terms of that contract permit the employer to make such a variation For further information, see Practice Note: TUPE—variation of contract