Calculate CGST, SGST, IGST as per section 88A

calculateTaxToBePaid.js

var Ip = 500, // Payable IGST
	Cp = 500, // Payable CGST
	Sp = 500, // Payable SGST
	Ic = 200, // IGST Credit
	Cc = 400, // CGST Credit 
	Sc = 700; // SGST Credit

// Calculate Tax as per Section 88(A)

function calculateTaxToBePaid(Ip,Cp,Sp,Ic,Cc,Sc) {
	
	var result = [];
	var taxToBePaid = { "SGST" : 0, "CGST" : 0, "IGST" : 0 };
	var creditLeft = { "SGST" : 0, "CGST" : 0, "IGST" : 0 };
	var I = Ic-Ip;
	var C = 0;
	var S = 0;
	
	result["TaxToBePaid"] = taxToBePaid;
	result["CreditLeft"] = creditLeft;
	
	if( I > 0 ) { // IGST is remaining
		if( Sc-Cc > 0 ) { // SGST credit is more
			Cp = I > (Sc - Cc) ? (Cp - (Sc - Cc)) : (Cp - I) // adjust IGST leftover in SGST
			I = ( I - (Sc - Cc) ) > 0 ? I - (Sc - Cc) : 0;
			
		} else if(Sc-Cc < 0){
			Sp = I > (Cc - Sc) ? Sp - (Cc - Sc) : Sp - I // adjust IGST leftover in CGST
			I = ( I - (Cc - Sc) ) > 0 ? I - (Cc - Sc) : 0;
			
		} 		
		
		// adjust IGST to both SGST and CGST;
		if( I > 0 && (I/2 < Sp) ) {
				Sp = Sp - I / 2;
				Cp = Cp - I / 2;
				I = 0;
		} else {
			I = I - Sp * 2;
			Sp = Cp = 0;
		}
		
		Ic = I;
	} 

	S = Sc - Sp >= 0 ? 0 : Sp - Sc;
	C = (Cc - Cp >= 0) ? 0 : (Cp - Cc);
	Sc = Sc - Sp > 0 ? Sc - Sp : 0;
	Cc = Cc - Cp > 0 ? Cc - Cp : 0;
	
	// If after adjusting CGST and SGST, remaining credit amount can be adjusted with IGST
	if( I < 0 ) {
		Ic = 0;
		I = -I;
		
		if((I) >= Sc ) {
			I = ((I) - Sc) ;
			Sc = 0;
		} else {
			Sc = Sc - (-I);
			I = 0;
		}
		
		if( I > 0 ) {
			if((I) >= Cc ) {
				I = ((I) - Cc) ;
				Cc = 0;
			} else {
				Cc = Cc - (I);
				I = 0
			}
		}
	}
	taxToBePaid["SGST"] = S;
	taxToBePaid["IGST"] = I;
	taxToBePaid["CGST"] = C;
	
	creditLeft["SGST"] = Sc;
	creditLeft["IGST"] = Ic;
	creditLeft["CGST"] = Cc;
	
	return result;
}

//console.log(calculateTaxToBePaid(Ip,Cp,Sp,Ic,Cc,Sc));
calculateTaxToBePaid(Ip,Cp,Sp,Ic,Cc,Sc); // [ TaxToBePaid: { SGST: 0, CGST: 100, IGST: 100 }, CreditLeft: { SGST: 0, CGST: 0, IGST: 0 } ]