Abstract Most estimates of the welfare costs of inflation are devised considering only noninterest-bearing assets, ignoring that since the 1980s technological innovations and new regulations have increased the liquidity of interest-bearing deposits. We investigate the resulting bias. Sufficient and necessary conditions on its sign are presented, along with closed-form expressions for its magnitude. Two examples dealing with bidimensional bilogarithmic money demands show that disregarding interest-bearing monies may lead to a non-negligible overestimation of the welfare costs of inflation. An intuitive explanation is that such assets may partially make up for the decreased demand of noninterest-bearing assets due to higher inflation.