I made an online claim for medical expenses last week and today my husband received a p21 cos he is the assessable spouse. It says we underpaid tax. My husband worked for 3 different employers last year. The income part of the form lists the earnings from one of the employers twice quoting exactly the same total income for both listings. Basically it says he earned 3227 euro with them between 5th april and 21st may and then 3227 euro with them between 20th and 21st may. This is wrong, he earned 3227 with them in total. When you take this into account in relation to everything else on the p21 we are due a refund of 161 euro. How do I go about sorting things out? Is a p21 a final statement or can it be changed? How to I get proof of the mistake?