Paying your Self Assessment Tax bill: https://www.gov.uk/pay-self-assessment-tax-bill

Paying your PAYE bill: https://www.gov.uk/pay-paye-tax

Paying your VAT bill: https://www.gov.uk/pay-vat

Paying your corporation tax bill: https://www.gov.uk/pay-corporation-tax

If you cannot pay your tax bill in full : https://www.gov.uk/difficulties-paying-hmrc

The Pension Regulator: https://www.thepensionsregulator.gov.uk/

Invest Ni: https://www.investni.com/

Ni Direct: https://www.nidirect.gov.uk/