EBITDA

EBITDA, or earnings before interest, taxes, depreciation and amortization, is a measure of profitability.

https://www.investopedia.com/terms/e/ebitda.asp

The Formula for Earnings Before Interest, Taxes, Depreciation and Amortization (EBITDA) Is:

EBITDA = Net Income + Interest + Taxes + Depreciation + Amortization

or

EBITDA = Operating Income + Depreciation + Amortization

Interest

The interest in EBITDA refers to the net interest difference between interest paid on debt and interest received from investments. 

Taxes

Taxes vary and depend on the region where the business is operating.

The benefit of the RDEC scheme is that it sits "above" the Operating Income line and is included in EBITDA calculation. RDEC increases company's EBITDA by 12% of qualifying expenditure.