Attendance at QMUL

I'm 3rd year maths at QMUL, just wondering if anyone knows about attendance being monitored this year. In second year I missed a few lectures and was never contacted about anything so assume it wasn't an issue, but I've just seen we now have attendance codes. I haven't put any of these in so far, so currently have 0% attendance for this year?
Does anyone know how these work or if they were in use last year while I was on placement? I don't even bring my phone half the time, is it likely they will be monitored/checked?