Int on Gross or Net if output declared in next tax period

If any gst output liability which was erroneously left while filing return of that period, so is shown in next tax period. In that case will the interest for delayed payment be calculated on gross amount or net of ITC...?
Some are of opinion that net liability to be used only if output declared in respective return only but return was delayed. In case eg may 20 sales shown in june 20 return then int on gross to be paid. Ref sec 50(1) which quotes 'declared in return for the said tax period'