1) both would have equal share in flat 

2) buyer will deduct TDS from your and mother in law share separately 

In absence of any indication the share in sale proceeds will be equal 

The buyer can deduct tds on entire sale proceeds either from the share of one co owner and from the share of each co owner 

The capital gains have to be invested in purchase of another residential house to save capital gains tax. It does not matter what is the source of money for this purchase. Just the entire capital gains need to be reinvested. 

As tds will be deducted and you will also be buying a new house, the seller parties can claim refund of tax in their income tax returns 

Since there is no particular mention about each individual's share in the registered sale deed, it is understood that both have equal share in the property.

If you both are filing the ITR separately then it would be advisable you have the TDS certificate on each individual's name instead of a joint TDS certificate. 

TDS in case of joint owners is deductible only in case sale proceeds in respect of each owner exceeds 50L. If the sale consideration is 1 Cr. and share of one owner is 40L no TDS will be deducted for him. The owner having share of 60L will be paying TDS on 10L. Each owner has to show separate receipt for TDS liability and capital gain exemption.

It will be considered as 50 percent each if no share mentioned. Tax liability will be accordingly decided

If in previous sale deed share ratio is not mentioned than by default it's equal sharing ratio 50-50%.

Buyer can't deduct TDS here. You can take whole amount from buyer. You have to show that sell amount has been invested in Government Bonds, NABARD or real estate.

And you will get rebate on inflation amount for reinvesting in the new property.

 For reinvesting you have two years time from date of sale or pre sale one year you can show invested amount.

Dear Client,

TDS on property sale is deducted on total consideration irrespective of No of Buyers or Sellers & their respective contribution in the property. If the property value is more than 50 Lacs than irrespective of No. of Buyer or Sellers, TDS will be deducted by Buyer/s. All Buyers/Sellers will fill/receive separate forms/TDS certificates.

Thank You.

-  Since, the said flat is  jointly in the name of you and mother-in-law ,it means you both having equal share in the flat, i.e. 50% each 

-  Further, as you both required to appear before the Registrar for executing the sale document in favor of purchaser , and the sale proceed will also shared equally between you and her. 

- Hence, the buyer can deduct TDS on the shared value, so that you both can show the TDS in the income tax separately. 

- Further , you both can reinvest the capital gain jointly. 

It has to be presumed that you both have equal shares. You need to split the sale proceeds equally and each has to account for capital gains separately. Please take the advice of a tax consultant too.