Self employed income

I was full time employee for the first six months, and then changed to self-employed contractor issuing an invoice to a seperate but related entity. What are the deductions I can claim against income invoiced?

Do you still only receive income from that one company or do you work for others and receive additional income?

I also am sole shareholder in a transport company, but do not draw a salary. Payments to myself charged against credit loan account

The company will be able to claim all the costs of doing business which it incurs in earning that income.