1) Deduction at source means deduction of tax at the time of payments against
supplies/services/services under contract/commission etc by the buyer being a withholding agent and deposit with the Government treasury within 7 days of the following the week in which deduction was made.

2) Advance payment of tax means payment of tax in advance in 4 four installments (quarterly) in respect of current year liability.
1st Installment - 25th September
2nd Installment - 25th December
3rd Installment - 25 March
4th Installment - 15 June

3) Payment of tax while filing the income tax return.
Total liability - Advance tax payment = Tax Payable and tax payable will be
deposited under section 137(1) of the Income Tax Ordinance, 2001

4) Payment of tax on demand by authorities means amount of tax required to be deposited after amended assessment.

5) Recovery through tax recovery procedure, if taxpayer fails to pay tax on demand - recovery under section 138(2) read with recovery rules under Income tax rules, 2002.