When you claim the Homecarers credit your client will either:
Get the credit, and lose the increased standard rate band for married people
or
They will keep the increased standard rate band for married people, and not receive the credit.
They application will work out which is more beneficial for your client. If the spouse’s income is less than €3,600, then it is better for your client to get the credit. If the spouse’s income is equal to, or greater than, €3,600, then it is better for the client to keep the increased standard rate band for married people, and not get the credit.