It sure looks like you know little about socialism
Unfortunately the right conflated Labour's social democratic post-war project with Stalinism and worse, and so the term socialism in common usage, covers a multitude of sins.
Even Wiki has two different pages for socialism and socialism (Marxism). So I think it is safe to assume that the tag covers a spectrum of political models.
The recent Daily Mail attack on Ralph Miliband who was a Marxist, was used to accuse Red Ed of being the same, by describing him as a socialist, in the full knowledge that readers would predictably conflate the two.
So taking that into account I would say that New Labour's project was Social Democracy light, which dispensed with the nationalisation and national industrial planning but kept wealth distribution, social security, the minimum wage and Keynesian demand management.
So if you accept that social democracy is driven by socialist values, and that wealth redistribution is one of those values, then you probably have to accept that tax-credits are a socialist intervention.