Manoj buys a lather coat costing Rs 900 at Rs 990 after paying the VAT.

Let the rate of VAT be $x \%$.

Then,

VAT $=$ Rs. $\left(\frac{x}{100} \times 900\right)$

$=$ Rs. $9 x$

So,

$900+9 x=990$

$9 x=90$

$x=10$

Thus, Manoj was charged $10 \%$ VAT on the leather jacket.