They are treated together and the full amount is taken into consideration. You do your income tax return and your full income is taken into consideration. You will not receive both earned income credit and PAYE credit. So as your full income would be about 60K, your first 40K would be taxed at 20% and the remaining at 40%. However, as your 2021 income was 25K, your spouse should have benefited from an increased tax band (at 20%), which would not be the case if your income increases to 60K.