@Laalmon – yes, you can have numerous W2s and 1099s on a single tax yea, no problem at all. As for your tax liability for the time they pay (or paid) with 1099s, your FICA taxes will be Amount*15.3%  (all other taxes will remain same). Did you see a 15.3% increase in your pay? (7.65% their share and 7.65% your portion withheld). If you didn’t see a 15.3% increase in your pay, they have lowered your pay.