Turbo Tax is very conservative and doesn't want you to owe too much next year. If you are receiving a refund or low tax due and Turbo Tax prepared the vouchers then your tax liability was probably reduced by credits. They might have printed out if you got a one time large income this year like if you took a IRA or 401k distribution. They are optional to pay and do not get sent with your return so the IRS won't be expecting them.
