Sentence:  HMRC said that one reason they had not <WSD>actioned</WSD> her appeal was because she had said in her appeal form ‘I am appealing against the overpayment for childcare for 2003-04, 2004-05', thus implying she was disputing her ‘overpayment'. 
Meaning of the word marked with <WSD> tags:  To act on a request etc, in order to put it into effect.