It would depend on whether or not the pension premiums were deductible when your late wife paid them. If they were then the payouts now would be taxable. I'm assuming you receive this amount as an annuity each month? Tax does get paid on annuity income so depending on the amount and your age there may be an amount that is still taxable.
If you would like to send the calculation to firstname.lastname@example.org I would be very happy to have a look for you.
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