6. No action may be instituted by a municipality under the In Rem Tax Foreclosure Act (1948), P.L.1948, c.96 (C.54:5-104.29 et seq.), on any tax sale certificate unless:
a. More than six months have expired from the date of the tax sale out of which any such certificate arose; and
b. All or any portion of the general land taxes levied and assessed against the land for 21 months next preceding the commencement of the action, other than those subject to payment by installments authorized by a resolution adopted pursuant to R.S.54:5-65, remains unpaid.
Such action on a tax sale certificate may include the lien for unpaid taxes, utility liens or any other municipal liens in conjunction with or independent of one another.