Prof. Damodaran (look him up) uses free cash flow to the firm (FCFF) when comparing cash flows to enterprise value (the value of operating assets). When comparing equity value, he uses free cash flow to equity (FCFE) which is basically FCFF less debt service i.e. cash flow available for distribution to shareholders or to repurchase shares.
For FCFF, Damodaran uses EBIT * (1-t) less capex less change in working capital. So, to answer your question, I would reduce your cash flow by taxes. If you don't want to use the above formula, you can always use cash taxes paid, which is usually disclosed as a supplement to the cash flow statement.
If you forecast FCFF, you can discount those cash flows at the firm's cost of capital to get to an implied enterprise value (then back off debt and add cash to get to equity value). The cost of capital of the firm (discount rate) is where the tax benefit of paying interest gets factored in. For example, if the firm's cost of debt is 10%, tax rate is 30% and they are levered 40% debt to total capital, the after-tax (effective) cost of debt is 10% * (1 - 30%) = 7%, which would comprise 40% of your total cost of capital.
So yeah, not trying to get in the weeds here, but I would incorporate tax expense into your cash flow figure.