Logged into my online account to change my address and noticed my salary was about £1500 more than it actually is. I had always suspected I was being underpaid by about £60-£70 a month (according to the calculators). No idea how I didn't notice this before as I have them my P60 figure last year.
I called them and they have now amended it. My payments from April onwards have gone up by £60 but I was told I should receive a back payment but no mention of this.
My next 2 payments (March and April) are called 'one-off' payments but they are just the same as my normal payments.
I can't face ringing them again......