20. Trade and other receivables and contract assets
20.1 Trade and other receivables
  Group   Company  
  31 March 
2020 
Rm 		   31 March 
2019 
Rm 		   31 March 
2020 
Rm 		   31 March 
2019 
Rm 		  
  7 019    7 425    6 197    8 427   
Trade receivables 4 867    5 884    4 678    5 278   
   Gross trade receivables 6 744    7 091    5 871    6 283   
   Impairment of receivables (1 877)   (1 207)   (1 193)   (1 005)  
Other receivables 1 794    854    1 394    2 668   
Prepayments 358    687    125    481   

Trade receivables are amounts due from customers for goods sold or services performed in the ordinary course of business. The repayment terms of trade receivables vary between 21 days and 90 days from date of invoice. Interest charged on overdue accounts varies between a rate of prime and a rate of 18%, depending on the contract terms.

Trade receivables are recognised initially at the transaction price, unless they contain significant financing components, in which case they are recognised at fair value.

Other receivables generally arise from transactions outside the usual operating activities of the Group.

  Group   Company  
  31 March 
2020 
Rm 		   31 March 
2019 
Rm 		   31 March 
2020 
Rm 		   31 March 
2019 
Rm 		  
Allowance account for credit losses - trade receivables 1 877    1 207    1 193    1 005   
   Opening balance as previously reported 1 207    827    1 005    602   
   Adoption of IFRS 9 Financial Instruments - Adjustment to allowance account measurement –    (61)   –    (48)  
   Adoption of IFRS 9 Financial Instruments - Change to write-off criteria –    559    –    559   
   Charged to statement of profit or loss and other comprehensive income 795    184    418    208   
   Enterprise loss allowance movement –    –    (18)   (105)  
   Receivables written off (125)   (302)   (212)   (211)  

Trade receivables are written off when there is no reasonable expectation of recovery. Indicators that there is no reasonable expectation of recovery include, amongst others, the failure of a debtor to engage in a repayment plan with the Group, and a failure to make contractual payments for a period ranging between 90 days past due and 180 days past due, based on the customer segment.

Refer to note 15.3 for detailed credit risk analysis.
20.2 Contract assets
  Group   Company  
  31 March 
2020 
Rm 		   31 March 
2019 
Rm 		   31 March 
2020 
Rm 		   31 March 
2019 
Rm 		  
Contract assets 1 979    2 161    1 850    2 161   
   Gross contract assets 2 411    2 331    2 281    2 331   
   Impairment of contract assets (432)   (170)   (432)   (170)  
Allowance account for credit losses - contract assets 432    170    432    170   
   Opening balance as previously reported 170    95    170    95   
   Charged to statement of profit or loss and other comprehensive income 345    200    345    200   
   Contract assets written off (83)   (125)   (83)   (125)  

Contract assets are written off when there is no reasonable expectation of recovery. Indicators that there is no reasonable expectation of recovery include, amongst others, the failure of a debtor to engage in a repayment plan with the Group, and a failure to make contractual payments for a period ranging between 90 days past due and 180 days past due, based on the customer segment.

Refer to note 15.3 for detailed credit risk analysis.

Significant changes in contract assets

The decrease in the net contract assets is due to an increased impairment amount recognised in the current financial year.