The Connecticut Department of Revenue Services doesn't support electronic filing of returns, estimates, or extensions for corporations filing on a 52 or 53 week tax year, amended combined, powers of attorney, or the bi-annual business entity tax return through the Modernized E-file system. You still need to file amended returns electronically through Connecticut's
taxpayer service center (TSC) unless the taxpayer is granted a waiver upon completing and filing Form DRW-EWVR, Electronic Filing and Payment Waiver Request. The Commissioner of the Connecticut Department of Revenue Services has revoked the mandate to file Form OP-424 electronically at this time.