Tax on employee share scheme

If you leave a company before the tax year end and sell the shares, receiving the income before the tax year ends and pay basic rate of tax, but the company subsequently puts that through on your wage slip as in the new tax year, when you are now a higher rate tax payer at a new company, do you have to pay higher rate on those funds? Additionally, although the trustee managing the scheme has said all of the funds were sold in the prior tax year, the company you worked for then pays a small portion it underpaid you in the new tax year, do you have to pay tax on the full sale of the shares?

Hi James,
ERSM20193 advises: The RSU may pay out what are often referred to as “dividend equivalents” in either cash or shares and such payments may be rolled up and paid out at the time the RSU vests or paid out on a regular basis, perhaps to match the payment of actual dividends on shares in the company. Such payments will generally be taxed as earnings in the year they are received.  
ERSM20193 - Employment-related securities and options: what are securities: RSUs and dividend equivalents.
Thank you.