Appellant contends that the Tax Commissioner’s letter, given before an audit and without specification of claimed deficiencies, is not proper notice to start the running of the 60-day period within R. C. 5739.03. That section, in pertinent part, provides:
“If any sale is claimed to be exempt * * * the consumer must furnish to the vendor, and the vendor must obtain from the consumer, a certificate specifying the reason that the sale is not legally subject to the tax. * * * If no certificate is furnished or obtained within the period for filing *152the return for the period in which such sale is consummated, it shall be presumed that the tax applies. The failure to have so furnished, or to have so obtained, a certificate shall not prevent a vendor or consumer from establishing that the sale is not subject to the tax within sixty days of the giving of notice by the commissioner of intention to levy an assessment, in which event the tax shall not apply.”
This court has often stated that statutory exemptions from a tax must be strictly construed, and one claiming an exemption must affirmatively establish his right thereto. National Tube Co. v. Glander (1952), 157 Ohio St. 407, 105 N. E. 2d 648; Goldman v. Robert E. Bentley Post No. 50 (1952), 158 Ohio St. 205, 107 N. E. 2d 528, Canton Malleable Iron Co. v. Porterfield (1972), 30 Ohio St. 2d 163, 283 N. E. 2d 434. It is evident from a literal reading of R. 0. 5739.03, that the notice of an intention to levy an assessment may be given before an audit has been completed.
Appellant also urges that the letter in the present case was not proper notice because it did not specifically state what the deficiencies were. It is argued that the company could not, from the notice, ascertain what exemption certificates the agent found to be missing. In Union Metal Mfg. Co. v. Kosydar (1974), 38 Ohio St. 2d 53, 310 N. E. 2d 249, it is noted that a taxpayer has the burden of affirmatively establishing sales tax exemption by obtaining the necessary exemption certificates. Once such certificates are not timely furnished or obtained, it is presumed that the sales are taxable. R. C. 5739.03. If the taxpayer fails to meet the statutory obligations concerning the certificates, he is allowed the 60-day period to obtain “letters of usage” establishing exception from the tax. In that context, it is the taxpayer who is in a position to know from which customers he has failed to obtain the proper exemption certificates. Furthermore, the record reflects the fact that appellant did procure many “letters of usage” from other customers before the end of the 60-day period.
We are aware of the erroneous statements alleged to have been made by appellee’s agent, which may have play*153ed a part in appellant’s failure to get all of the “letters of usage” within the time prescribed by R. C. 5739.03. As a general rule, however, the principle of estoppel does not apply against the state with regard to a taxing statute. Recording Devices v. Bowers (1963), 174 Ohio St. 518, 190 N. E. 2d 258; Interstate Motor Freight System v. Donahue (1966), 8 Ohio St. 2d 19, 221 N. E. 2d 711.
The duty imposed upon a taxpayer who neglects to obtain exemption certificates is clear; 60 days is provided, from the notice of intention to levy an assessment, to overcome the presumption that the tax applies. This was unambiguously expressed in the letter of March 3, 1972, and appellant’s failure to obtain the “letters of usage” within the 60-day period stems from its disregard of the specific mandates of that letter and R. C. 5739.03.
The decision of the Board of Tax Appeals is affirmed.
Decision affirmed.
0 ’Neill, C. J., Herbert, Stern, Celebrezze, W. Brown and P. Brown, JJ., concur.