40(a)

TDS deductible in the month of March 2009 and paid before the due date of filing of return is not disallowed u/s 40(a)(ia). However if TDS deductible in months before March and deducted in March and paid after 31st March, 2009 will be allowed in F. Y. 2009 - 10 or the year in which payment is made.

So in your case since TDS was not deducted for the whole year and deducted in march only and paid in May Rs. 137,500/- (12500 * 11) will be disallowed u/s 40(a)(ia) and will be allowed in F. Y. 2009 - 10 and march rent will be allowed in the same F. Y. only.