We are getting one or two clients who have a reasonable idea of current year income, but no idea about the previous year. On the basis of current year income they are entitled to maximum TC. If this is so, is there any need to try to find out what the previous year income was? We think not, but are a bit wobbly.

The rationale is that the previous years taxable income is only used if it is slightly less than the current year. Whilst its true that not all the TC computation components went up by the same amount for inflation, we reckon that in most cases a calculation based on the current year will be right, again assuming that the claimant comes out entitled to the maximum.

This still leaves the problem of the IR not having full data, but is this a shortcut?

This should be fine. The income eventually taken into account cannot exceed actual CY income .If CY income is below the threshold anyway, then PY income cannot make any difference.

(remember not to allow any 2500 disregard when calculating CY income - the safe assumption is that the unknown PY is at least equal to CY income).

Only disadvantage is that you can't give your clients any idea of how much their CY income could rise before the CY/PY disregard (if any) is used up and they risk overpayment.

Awards are always calculated on CY income, PY income is only used as a guidline.