I am a separated father of one child who stays with me most weekends. My estranged wife works part time now and again. She is also in receipt of carers allowance and other benefits. We are currently assessed as a married couple but Tax returns are a nightmare because of (1) the breakdown in the marriage (not very cordial) and (2) the variability of ex-wife income. Would there be much in the difference if we were treated as single people for Tax purposes. I work full time and earn 40K.