A method for determining the nucleotide sequence of a single-stranded nucleic acid molecule comprising: (a) contacting the single-stranded nucleic acid molecule, wherein the single-stranded nucleic acid molecule is in an electrolyte solution in contact with a nanopore in a membrane and wherein the single-stranded nucleic acid molecule has a primer hybridized to a portion thereof, with a nucleic acid polymerase and at least four phosphate-tagged nucleotide polyphosphate analogues under conditions permitting the nucleic acid polymerase to catalyze incorporation of one of the NPP analogues into the primer if it is complementary to the nucleotide residue of the single-stranded nucleic acid molecule which is immediately 5' to a nucleotide residue of the single-stranded nucleic acid molecule hybridized to the 3' terminal nucleotide residue of the primer, so as to form a nucleic acid extension product and with the proviso that (i) the type of base on each NPP analogue is different from the type of base on each of the other three NPP analogues, and (ii) either the number of phosphates in the polyphosphate portion of each NPP analogue is different from the number of phosphates in the polyphosphate portion of each of the other three NPP analogues, or the number of phosphates in the polyphosphate portion of each of the four NPP analogues is the same and the type of tag on each NPP analogue is different from the type of tag on each of the other three NPP analogues, wherein incorporation of the NPP analogue results in release of a polyphosphate having the tag attached thereto; and (b) determining which NPP analogue has been incorporated into the primer to form a nucleic acid extension product in step (a) by applying a voltage across the membrane and measuring an electronic change across the nanopore resulting from the polyphosphate having the tag attached thereto generated in step (a) translocating through the nanopore, wherein the electronic change is different for each number of phosphates in the polyphosphate portion, or for each different type of tag, as appropriate, thereby identifying the nucleotide residue in the single-stranded nucleic acid complementary to the incorporated NPP analogue; and (c) iteratively performing steps (a) and (b) for each nucleotide residue of the single-stranded nucleic acid molecule being sequenced, wherein in each iteration of step (a) the NPP analogue is incorporated into the nucleic acid extension product resulting from the previous iteration of step (a) if it is complementary to the nucleotide residue of the single-stranded nucleic acid molecule which is immediately 5' to a nucleotide residue of the single-stranded nucleic acid molecule hybridized to the 3' terminal nucleotide residue of the nucleic acid extension product, thereby determining the nucleotide sequence of the single-stranded nucleic acid molecule. (a) contacting the single-stranded nucleic acid molecule, wherein the single-stranded nucleic acid molecule is in an electrolyte solution in contact with a nanopore in a membrane and wherein the single-stranded nucleic acid molecule has a primer hybridized to a portion thereof, with a nucleic acid polymerase and at least four phosphate-tagged nucleotide polyphosphate analogues under conditions permitting the nucleic acid polymerase to catalyze incorporation of one of the NPP analogues into the primer if it is complementary to the nucleotide residue of the single-stranded nucleic acid molecule which is immediately 5' to a nucleotide residue of the single-stranded nucleic acid molecule hybridized to the 3' terminal nucleotide residue of the primer, so as to form a nucleic acid extension product and with the proviso that (i) the type of base on each NPP analogue is different from the type of base on each of the other three NPP analogues, and (ii) either the number of phosphates in the polyphosphate portion of each NPP analogue is different from the number of phosphates in the polyphosphate portion of each of the other three NPP analogues, or the number of phosphates in the polyphosphate portion of each of the four NPP analogues is the same and the type of tag on each NPP analogue is different from the type of tag on each of the other three NPP analogues, wherein incorporation of the NPP analogue results in release of a polyphosphate having the tag attached thereto; and (b) determining which NPP analogue has been incorporated into the primer to form a nucleic acid extension product in step (a) by applying a voltage across the membrane and measuring an electronic change across the nanopore resulting from the polyphosphate having the tag attached thereto generated in step (a) translocating through the nanopore, wherein the electronic change is different for each number of phosphates in the polyphosphate portion, or for each different type of tag, as appropriate, thereby identifying the nucleotide residue in the single-stranded nucleic acid complementary to the incorporated NPP analogue; and (c) iteratively performing steps (a) and (b) for each nucleotide residue of the single-stranded nucleic acid molecule being sequenced, wherein in each iteration of step (a) the NPP analogue is incorporated into the nucleic acid extension product resulting from the previous iteration of step (a) if it is complementary to the nucleotide residue of the single-stranded nucleic acid molecule which is immediately 5' to a nucleotide residue of the single-stranded nucleic acid molecule hybridized to the 3' terminal nucleotide residue of the nucleic acid extension product,