If you have an ILR UK stamp on your expired passport then you can use it to travel outside the UK and come back but will also need a current, valid passport. You cannot use your expired passport when you are asked to undergo the right to work checks since the ILR may be active but because your passport is expired you may face certain complications as you won’t be able to use your expired passport.If your ILR endorsement is on your expired passport, then the wiser way would typically be to make a “No time limit application” to transfer your details to a Biometric Residence Permit (BRP). When you are making an online application for ILR UK (Indefinite Leave to Remain) you are required to provide the UK visa and immigration with your valid passport as well as any other previous passport that you have held to confirm your identity. Read More: ILR on an expired passport