Tier 2 visa approved by background check being delayed

Hi

I have got Tier 2 visa and my CoS start date is 1st July. However, my employer is still conducting pre-employment screening and they told me it might take 6-8 weeks to process (I submitted first advantage online form on May 8th). My question is, can I enter UK on June 28 as planned? Will there be legal/tax complications if I remain in UK and wait for background check to be cleared (say it is cleared on 15 July and I officially start then)

Thank you!

There is no reason not to travel before the internal clearance from your employer. If fact if you only have the 30 day travel vignette to travel in any case.