Lloyds TSB tax certificate error

This affects people who received TSB's Save the Change incentive in 2006/07 and 2007/08.

TSB paid participants two incentives up to a maximum of £50 in the March and April 2007 respectively. They paid the incentive net of tax.

The tax certificate for 2006/07 reflects the March incentive. The tax certificate for 2007/08 doesn't.

1. Why did they deduct tax at source in the first place? I have never seen an incentive payment treated as if it was interest.
2. If interest was deducted at source, the 2007/08 certificate needs to be amended. Otherwise, people who pay less than 20% tax in that year can't claim it back.

It's a pretty sad state of affairs if yiou can't even rely on interest calculations being correct (see Lloyds Classic Plus 6% - is your interest correct this month?).