Possible Clues:

• One of two certainties in life
• Puts an onus on
• Puts great strain on, as Revenue Commissioners do
• April 15 payments
• Levies, strains
• A certain thing Tory leader cuts
• Pay stub data
• "Nothing's truer than them": "David Copperfield"
• Subject of Article I, Section 8 of the Constitution
• One of two 'certainties' in life