This image explains how you calculate threshold income and adjusted income.
For threshold income include all earnings and investment income, deduct gross member contributions whether under relief at source or net pay arrangement, add any employment income given up through a salary exchange agreement set up after 8 July 2015 and finally deduct any taxed lump sum death benefit received. For adjusted income include all earnings and investment income, add any employer contributions and finally deduct any taxed lump sum death benefits received.