Your franking machine warranty is protected under the OFT Act of 2002 and further undertakings given in 2005. This prohibits manufacturers from voiding a franking machine warranty due to the use of third party supplies. This ruling from the Office of Fair Trading means you are entitled to source your ink from your choice of supplier and this CANNOT and WILL NOT affect your service or warranty. The OFT undertakings can be seen
. If your manufacturer or one of their engineers tells you that use of any alternative ink cartridge will invalidate your warranty then they are breaking the law: this is illegal. Simply ask them to put it in writing and you will find that they will not.