Here are samples from my own custom letter:

[@FDIEFApp] $<@FDIEFApp> overpayment will be applied to your <@FDINxtYear> estimated taxes.
[@FDIEFDDep] $<@FDIEFRef> overpayment will be refunded.
[@FDIEFDDNo] $<@FDIEFRef> overpayment will be refunded.
[@FDIAppEst] $<@FDIAppEst> overpayment will be applied to your <@FDINxtYear> estimated taxes.
[@FDIEFDwP] $<@FDIEFDwP> balance due payable to the U.S. Treasury.
[@FDINoTax] There is no tax due or refund with this income tax return.
[@FDIEFNoTax] There is no tax due or refund with this income tax return.

I also add in the direct deposit info into my letter.

Please verify. [@FDIBank]<@FDIBank>, routing #[@FDIRTN]<@FDIRTN> and account #[@FDIAcctNo]<@FDIAcctNo>.