As you have a partner I assume this is a joint claim. If the two of you together are working total of 30 hours p wk & one of you is working 16 or more, then there is still an entitlement to WTC. So if your hours reduce from 16 to (say) 10 & your partner works 20, WTC can continue. What you lose is the disabled element. If you have a child I think the 30 hours goes down to 24 (again, for the two of you together).