Much depends on the facts of each case.The general trend in the dept is that rental income from commercial shops are taxed u /s 22. But a view is also possible where the letting is done on such a scale with so many connected activities and provision of amenities that the income is assessable as business income. If there is evidence of intention to exploit the property commercially then the chances are more that it can be assessed u /s 28. Or you can atleast plead for bifurcation of income between pure rental income and other income representing consideration for use of common facilities like lifts, parking space, common security etc. You can refer the decision of the Hon' High court of kerala in Attukal shopping complex case.
Regarding letting of plot Sec22 is not at all attracted as there is no building. Then it can be assessed as business income or under other sources and you may apply the usual principles to decide the head. siva208@yahoo.com