diff --git a/src/contracts/bsv20BuyLimitOrder.ts b/src/contracts/bsv20BuyLimitOrder.ts
index bd045409..dbc1d50a 100644
--- a/src/contracts/bsv20BuyLimitOrder.ts
+++ b/src/contracts/bsv20BuyLimitOrder.ts
@@ -71,8 +71,8 @@ export class BSV20BuyLimitOrder extends BSV20V2 {
 
         // Check that we're unlocking the UTXO specified in the oracles message.
         assert(
-            slice(this.prevouts, 0n, 36n) == slice(oracleMsg, 0n, 36n),
-            'first input is not spending specified ordinal UTXO'
+            slice(this.prevouts, 36n, 72n) == slice(oracleMsg, 0n, 36n),
+            'second input is not spending specified ordinal UTXO'
         )
 
         // Get token amount held by the UTXO from oracle message.
diff --git a/src/contracts/bsv20BuyOrder.ts b/src/contracts/bsv20BuyOrder.ts
index 3026fc20..5ccd4026 100644
--- a/src/contracts/bsv20BuyOrder.ts
+++ b/src/contracts/bsv20BuyOrder.ts
@@ -60,8 +60,8 @@ export class BSV20BuyOrder extends BSV20V2 {
 
         // Check that we're unlocking the UTXO specified in the oracles message.
         assert(
-            slice(this.prevouts, 0n, 36n) == slice(oracleMsg, 0n, 36n),
-            'first input is not spending specified ordinal UTXO'
+            slice(this.prevouts, 36n, 72n) == slice(oracleMsg, 0n, 36n),
+            'second input is not spending specified ordinal UTXO'
         )
 
         // Build transfer inscription.
diff --git a/src/contracts/bsv20CallOption.ts b/src/contracts/bsv20CallOption.ts
index a8212b61..0aa7694b 100644
--- a/src/contracts/bsv20CallOption.ts
+++ b/src/contracts/bsv20CallOption.ts
@@ -110,6 +110,9 @@ export class Bsv20CallOption extends BSV20V2 {
         // Check grantee sig.
         assert(this.checkSig(sigGrantee, this.grantee), 'invalid sig grantee')
 
+        // Check premium is a positive integer.
+        assert(premium > 0n, 'invalid premium value')
+
         // Store premium value in property.
         this.premium = premium
 
diff --git a/src/contracts/bsv20CouponBond.ts b/src/contracts/bsv20CouponBond.ts
index 15436334..8c6e75dd 100644
--- a/src/contracts/bsv20CouponBond.ts
+++ b/src/contracts/bsv20CouponBond.ts
@@ -101,8 +101,8 @@ export class Bsv20CouponBond extends BSV20V2 {
 
         // Check that we're unlocking the UTXO specified in the oracles message.
         assert(
-            slice(this.prevouts, 0n, 36n) == slice(oracleMsg, 0n, 36n),
-            'first input is not spending specified ordinal UTXO'
+            slice(this.prevouts, 36n, 72n) == slice(oracleMsg, 0n, 36n),
+            'second input is not spending specified ordinal UTXO'
         )
 
         // Get token amount held by the UTXO from oracle message.
@@ -113,7 +113,7 @@ export class Bsv20CouponBond extends BSV20V2 {
 
         // Check slot index is empty.
         const investor = this.investors[Number(slotIdx)]
-        assert(investor.emptySlot == true, 'slot is not empty')
+        assert(investor.emptySlot, 'slot is not empty')
 
         // Add to investors array.
         this.investors[Number(slotIdx)] = {
@@ -152,8 +152,8 @@ export class Bsv20CouponBond extends BSV20V2 {
 
         // Check that we're unlocking the UTXO specified in the oracles message.
         assert(
-            slice(this.prevouts, 0n, 36n) == slice(oracleMsg, 0n, 36n),
-            'first input is not spending specified ordinal UTXO'
+            slice(this.prevouts, 36n, 72n) == slice(oracleMsg, 0n, 36n),
+            'second input is not spending specified ordinal UTXO'
         )
 
         // For each investor add an output that pays them interest.
@@ -199,8 +199,8 @@ export class Bsv20CouponBond extends BSV20V2 {
 
         // Check that we're unlocking the UTXO specified in the oracles message.
         assert(
-            slice(this.prevouts, 0n, 36n) == slice(oracleMsg, 0n, 36n),
-            'first input is not spending specified ordinal UTXO'
+            slice(this.prevouts, 36n, 72n) == slice(oracleMsg, 0n, 36n),
+            'second input is not spending specified ordinal UTXO'
         )
 
         // For each investor add an output that pays them the face value token amount.
@@ -239,6 +239,9 @@ export class Bsv20CouponBond extends BSV20V2 {
             'invalid sig investor'
         )
 
+        // Check price value.
+        assert(price > 0n, 'invalid price value')
+
         // Toggle forSale flag and set price.
         this.investors[Number(slotIdx)].forSale = true
         this.investors[Number(slotIdx)].price = price
diff --git a/src/contracts/bsv20Loan.ts b/src/contracts/bsv20Loan.ts
index b8136b52..cbd9a0e8 100644
--- a/src/contracts/bsv20Loan.ts
+++ b/src/contracts/bsv20Loan.ts
@@ -75,7 +75,7 @@ export class Bsv20Loan extends BSV20V2 {
     @method()
     public borrow() {
         // Check loan isn't taken yet.
-        assert(this.taken == false, 'loan already taken')
+        assert(!this.taken, 'loan already taken')
         this.taken = true
 
         // Pay borrower the principal, i.e. token amount locked in the contract.
@@ -94,7 +94,7 @@ export class Bsv20Loan extends BSV20V2 {
     @method()
     public repay(oracleMsg: ByteString, oracleSig: RabinSig) {
         // Check loan is already taken.
-        assert(this.taken == true, 'loan not taken yet')
+        assert(this.taken, 'loan not taken yet')
 
         // Check oracle signature.
         assert(
@@ -104,8 +104,8 @@ export class Bsv20Loan extends BSV20V2 {
 
         // Check that we're unlocking the UTXO specified in the oracles message.
         assert(
-            slice(this.prevouts, 0n, 36n) == slice(oracleMsg, 0n, 36n),
-            'first input is not spending specified ordinal UTXO'
+            slice(this.prevouts, 36n, 72n) == slice(oracleMsg, 0n, 36n),
+            'second input is not spending specified ordinal UTXO'
         )
 
         // Get token amount held by the UTXO from oracle message.
diff --git a/src/contracts/bsv20LoanMultiple.ts b/src/contracts/bsv20LoanMultiple.ts
index 082c5392..292b14dd 100644
--- a/src/contracts/bsv20LoanMultiple.ts
+++ b/src/contracts/bsv20LoanMultiple.ts
@@ -101,7 +101,7 @@ export class Bsv20LoanMultiple extends BSV20V2 {
     ) {
         // Check slot index is empty.
         const borrower = this.borrowers[Number(slotIdx)]
-        assert(borrower.emptySlot == true, 'slot is not empty')
+        assert(borrower.emptySlot, 'slot is not empty')
 
         // Check borrower sig.
         assert(
@@ -130,8 +130,8 @@ export class Bsv20LoanMultiple extends BSV20V2 {
     public cancelRequest(slotIdx: bigint, borrowerSig: Sig) {
         // Check slot index is not empty and not yet approved.
         const borrower = this.borrowers[Number(slotIdx)]
-        assert(borrower.emptySlot == false, 'slot is empty')
-        assert(borrower.approved == false, 'request was already approved')
+        assert(!borrower.emptySlot, 'slot is empty')
+        assert(!borrower.approved, 'request was already approved')
 
         // Check borrower sig.
         assert(
@@ -169,8 +169,8 @@ export class Bsv20LoanMultiple extends BSV20V2 {
     ) {
         // Check slot index is not empty and not yet approved.
         const borrower = this.borrowers[Number(slotIdx)]
-        assert(borrower.emptySlot == false, 'slot is empty')
-        assert(borrower.approved == false, 'request was already approved')
+        assert(!borrower.emptySlot, 'slot is empty')
+        assert(!borrower.approved, 'request was already approved')
 
         // Check lender sig.
         assert(this.checkSig(lenderSig, this.lender), 'invalid sig lender')
@@ -204,8 +204,8 @@ export class Bsv20LoanMultiple extends BSV20V2 {
 
         // Check that we're unlocking the UTXO specified in the oracles message.
         assert(
-            slice(this.prevouts, 0n, 36n) == slice(oracleMsg, 0n, 36n),
-            'first input is not spending specified ordinal UTXO'
+            slice(this.prevouts, 36n, 72n) == slice(oracleMsg, 0n, 36n),
+            'second input is not spending specified ordinal UTXO'
         )
 
         // Get token amount held by the UTXO from oracle message.
@@ -239,7 +239,7 @@ export class Bsv20LoanMultiple extends BSV20V2 {
     ) {
         // Check slot index is not empty and approved.
         const borrower = this.borrowers[Number(slotIdx)]
-        assert(borrower.emptySlot == false, 'slot is empty')
+        assert(!borrower.emptySlot, 'slot is empty')
         assert(borrower.approved, 'borrow request not approved')
 
         // Check borrower sig.
@@ -256,8 +256,8 @@ export class Bsv20LoanMultiple extends BSV20V2 {
 
         // Check that we're unlocking the UTXO specified in the oracles message.
         assert(
-            slice(this.prevouts, 0n, 36n) == slice(oracleMsg, 0n, 36n),
-            'first input is not spending specified ordinal UTXO'
+            slice(this.prevouts, 36n, 72n) == slice(oracleMsg, 0n, 36n),
+            'second input is not spending specified ordinal UTXO'
         )
 
         // Get token amount held by the UTXO from oracle message.
@@ -294,7 +294,7 @@ export class Bsv20LoanMultiple extends BSV20V2 {
     public foreclose(slotIdx: bigint, lenderSig: Sig) {
         // Check slot index is not empty and approved.
         const borrower = this.borrowers[Number(slotIdx)]
-        assert(borrower.emptySlot == false, 'slot is empty')
+        assert(!borrower.emptySlot, 'slot is empty')
         assert(borrower.approved, 'borrow request not approved')
 
         // Check lender sig.
diff --git a/src/contracts/bsv20LockToMint.ts b/src/contracts/bsv20LockToMint.ts
index 10f5f07b..c3e9c6a8 100644
--- a/src/contracts/bsv20LockToMint.ts
+++ b/src/contracts/bsv20LockToMint.ts
@@ -53,7 +53,7 @@ export class BSV20LockToMint extends BSV20V2 {
         let outputs = toByteString('')
         let transferAmt = amount
 
-        if (this.supply - transferAmt > 0n) {
+        if (this.supply > transferAmt) {
             // If there are still tokens left, then update supply and
             // build state output inscribed with leftover tokens.
             this.supply -= transferAmt
diff --git a/src/contracts/bsv20Mint.ts b/src/contracts/bsv20Mint.ts
index cd97bcac..b19926d7 100644
--- a/src/contracts/bsv20Mint.ts
+++ b/src/contracts/bsv20Mint.ts
@@ -58,7 +58,7 @@ export class BSV20Mint extends BSV20V2 {
         let outputs = toByteString('')
         let transferAmt = amount
 
-        if (this.supply - transferAmt > 0n) {
+        if (this.supply > transferAmt) {
             // If there are still tokens left, then update supply and
             // build state output inscribed with leftover tokens.
             this.supply -= transferAmt
diff --git a/src/contracts/bsv20PutOption.ts b/src/contracts/bsv20PutOption.ts
index 842d48e7..0e65468b 100644
--- a/src/contracts/bsv20PutOption.ts
+++ b/src/contracts/bsv20PutOption.ts
@@ -80,8 +80,8 @@ export class Bsv20PutOption extends BSV20V2 {
 
         // Check that we're unlocking the UTXO specified in the oracles message.
         assert(
-            slice(this.prevouts, 0n, 36n) == slice(oracleMsg, 0n, 36n),
-            'first input is not spending specified ordinal UTXO'
+            slice(this.prevouts, 36n, 72n) == slice(oracleMsg, 0n, 36n),
+            'second input is not spending specified ordinal UTXO'
         )
 
         // Get token amount held by the UTXO from oracle message.
@@ -140,6 +140,9 @@ export class Bsv20PutOption extends BSV20V2 {
         // Check grantee sig.
         assert(this.checkSig(sigGrantee, this.grantee), 'invalid sig grantee')
 
+        // Check premium value.
+        assert(premium > 0n, 'invalid premium value')
+
         // Store premium value in property.
         this.premium = premium
 
diff --git a/src/contracts/bsv20SellLimitOrder.ts b/src/contracts/bsv20SellLimitOrder.ts
index a9a64551..97093841 100644
--- a/src/contracts/bsv20SellLimitOrder.ts
+++ b/src/contracts/bsv20SellLimitOrder.ts
@@ -66,13 +66,6 @@ export class BSV20SellLimitOrder extends BSV20V2 {
         // Update cleared amount.
         this.tokenAmtSold += amount
 
-        // Build transfer inscription.
-        const transferInscription = BSV20V2.createTransferInsciption(
-            this.id,
-            amount
-        )
-        const transferInscriptionLen = len(transferInscription)
-
         // Fist output is the contract itself, holding the remaining tokens.
         // If no tokens are remaining, then terminate the contract
         const tokensRemaining = this.tokenAmt - this.tokenAmtSold
diff --git a/src/contracts/bsv20ZeroCouponBond.ts b/src/contracts/bsv20ZeroCouponBond.ts
index 12971893..0c7b381b 100644
--- a/src/contracts/bsv20ZeroCouponBond.ts
+++ b/src/contracts/bsv20ZeroCouponBond.ts
@@ -101,8 +101,8 @@ export class Bsv20ZeroCouponBond extends BSV20V2 {
 
         // Check that we're unlocking the UTXO specified in the oracles message.
         assert(
-            slice(this.prevouts, 0n, 36n) == slice(oracleMsg, 0n, 36n),
-            'first input is not spending specified ordinal UTXO'
+            slice(this.prevouts, 36n, 72n) == slice(oracleMsg, 0n, 36n),
+            'second input is not spending specified ordinal UTXO'
         )
 
         // Get token amount held by the UTXO from oracle message.
@@ -116,7 +116,7 @@ export class Bsv20ZeroCouponBond extends BSV20V2 {
 
         // Check slot index is empty.
         const investor = this.investors[Number(slotIdx)]
-        assert(investor.emptySlot == true, 'slot is not empty')
+        assert(investor.emptySlot, 'slot is not empty')
 
         // Add to investors array.
         this.investors[Number(slotIdx)] = {
@@ -154,8 +154,8 @@ export class Bsv20ZeroCouponBond extends BSV20V2 {
 
         // Check that we're unlocking the UTXO specified in the oracles message.
         assert(
-            slice(this.prevouts, 0n, 36n) == slice(oracleMsg, 0n, 36n),
-            'first input is not spending specified ordinal UTXO'
+            slice(this.prevouts, 36n, 72n) == slice(oracleMsg, 0n, 36n),
+            'second input is not spending specified ordinal UTXO'
         )
 
         // For each investor add an output that pays them the face value token amount.
@@ -194,6 +194,9 @@ export class Bsv20ZeroCouponBond extends BSV20V2 {
             'invalid sig investor'
         )
 
+        // Check price value.
+        assert(price > 0n, 'price invalid value')
+
         // Toggle forSale flag and set price.
         this.investors[Number(slotIdx)].forSale = true
         this.investors[Number(slotIdx)].price = price