If you are withdrawing funds from an RRSP, you will pay tax immediately on withdrawal, and possibly more when you file your income tax return.
For example, if you take out $20,000 from your RRSP this year, after the 30% withholding ($6,000) is applied, you end up with $14,000. You will have to report this amount on your tax return as income. You may have to pay more tax on your income depending on your tax brackets.
If you transfer between RRSPs, tax will not be withheld.
Speak to your registered financial advisor or a tax professional about the tax consequences of RRSP withdrawals.