Yes, you can gross-up in Celery on 2 ways.
No open wage run may be present for this first option:
Go to the employee. You can see in your screen on the right the gross-up button.
With this option you can gross-up the fixed periodic salary. In that case Celery will add all the wage codes like reservation vacation allowance, pension premium, taxed fringe benefits car and phone etc. that are entered in this employee to the gross-up calculation.
The second and third option is the use of wage codes 180 and 190. Amounts entered in these wage codes are net amounts that will be grossed-up by Celery. These codes are often used for fixed net allowances and net bonuses. The difference between code 180 and 190 is that code 180 is also added to the SVB/SZV wage and code 190 isn't.