If the priorly set periodicity of a taxpayer is annual, and his tax liability recedes INR 50,000 as of the previous year, then he can change his PTRC's periodicity to monthly. On the other hand, if his periodicity has been monthly, under the same conditions he can change the PTRC to an annual periodicity. But, if the taxpayer has made a shift in periodicity from annual to monthly, and has already filed a return, then he will not be able to change the periodicity back.